Category Archives: Agriculture

We hope that future fabrication designs can benefit and improve on designs that work well

Through our assessment of lab-based chamber systems, we identify unique advantages and challenges associated with each system .Lastly, we offer our perspectives on areas in which technological advances are needed to fill current knowledge gaps.In studying rhizosphere processes, the myriad of complex interactions among members of the rhizosphere are often dissected to two interacting variables such as root-and-soil or root-and-microbes, etc. Each of these interactions inherently operates under distinct parameters and requires specifically designed platforms to effectively answer different research questions. This review is structured in a way that first describes each rhizosphere process briefly and then reports on the specific growth chamber systems designed to facilitate experiments for answering related research questions. The major rhizosphere processes discussed below include root system architecture, physicochemical gradients in the soil, exudation patterns by the roots and interactions between roots and nematodes, fungi or bacteria. Root system architecture encompasses structural features that provide spatial configuration such as root length, width, spread and number and is an important rhizosphere parameter in regulating soil porosity, and nutrient and water uptake efficiency by plants . Plants have been observed to “sense” and direct root growth toward nutrient sources in soil, and the RSA of a plant exhibits great malleability in response to environmental stimuli which in turn, influences microbial communities . For instance, bean plants grew deeper roots under drought conditions to enhance water foraging capabilities while low phosphate conditions stimulated the formation of dense lateral roots involved in P uptake from upper soil layers . Given that most soils are heterogenous,black plastic nursery pots understanding the RSA of plants becomes critical in improving resource use efficiency and agricultural yields . Often, RSA in pot-grown plants is investigated by excising the roots via mechanical means such as root washing or blowing with compressed air . These methods are, however, time-consuming, cause inevitable damage of fine root hairs and result in loss of spatial and temporal information .

An appealing alternative for studying RSA is the use of rhizotrons. Rhizotrons were initially constructed as underground facilities designed for viewing and measuring roots in the field . In the lab, the rhizotron implies a chamber constructed using two vertical sheets with at least one or both of the sheets being transparent and/or removable . This allows repeated visual inspections of individual roots; a feature unachievable with destructive sampling. In some cases, the word “rhizobox” is used for a similar set up although this was first introduced in as compartmentalized systems to separate the root and soil compartments . Rhizotrons/rhizoboxes are often constructed with PVC or acrylic materials and come in many sizes to accommodate different plants with soil or soil-less substrates . Root growth and morphology in the rhizotron can be tracked by a variety of methods ranging from manual tracing onto a plastic sheet, using handheld or flatbed scanners to fully automated time-lapse imaging camera systems . Data can be subsequently analyzed with a wide range of software packages . Affordable and robust RSA imaging platforms using rhizotrons have also been developed for increased accessibility in low-income countries . The versatile construction of a rhizotron design for RSA studies has inspired many variations. For instance, ara-rhizotrons were designed to enable the study of 3D canopy competition with simultaneous root growth observation in an Arabidopsis plant population . The horizontal and radial design of HorhizotronTM and mini-Horhizotron consisting of transparent quadrants attached to a central chamber were developed to study lateral growth of roots in a semi-3D space and to perform post-transplant assessment . The separated quadrants can also be used with different soil substrates simultaneously to study substrate effects on root growth . A rhizotron fitted with water-tight gasket seals has also been used successfully to investigate the RSA of plants under water-logged conditions . Despite the continuous real-time visual read-out, most rhizotron designs suffer from inevitable loss of information from roots occluded by soil particles. The GLO-Roots system overcomes this by imaging from both sides of the rhizotron while using bio-luminescent roots to create higher contrast against the soil, enabling quantitative studies on RSA . Following advances in engineering and device fabrication, more rhizotron variants adapted to specific plant growth conditions can be envisioned. In a typical topsoil, approximately half is composed of solid minerals and organic matter while the rest is a fluctuating composition of water and gas filled spaces influenced by environmental conditions and uptake/release of solutes from plants . Changes in gaseous and hydrologic parameters, such as ions, O2 and moisture among others, create a spatially complex environment that influences microbial communities and overall plant health.

These physicochemical fluxes are heterogeneously distributed along roots and vary with root types and zones . Often, they exist as gradients in the rhizosphere , thus emphasizing the need for non-destructive sampling in order to accurately capture processes occurring at biologically relevant times and scales. Rhizotron chambers with a visually accessible rhizosphere allows in situ and continuous mapping of these gradients in the soil through the use of different types of imaging methods. For instance, photo luminescence-based optical sensors enable in situ, repeated detection of small molecule analytes in addition to pH , O2 and NH4 . Methods like zymography to detect enzyme activity and diffusive gradients in thin film can be used to map solute concentrations in the soil down to sub-mm scales with high spatial resolution more realistically than traditional destructive approaches. For example, transport and distribution of water in the rhizosphere soil has been imaged on both 2D and 3D planes by coupling a rhizotron with neutron radiography and tomography, respectively and showed varying moisture gradients along the root system with higher water uptake at the rhizosphere compared to bulk soil. On the other hand, if the rhizotron slabs are thin enough , even simple imaging solutions based on light transmission can be set up to capture water uptake by roots in sand . Despite trade-offs in method sensitivity between these two studies, a rhizotron set up is critical in both designs and illustrates its adaptability to multiple equipment. Roots exude a substantial amount of photosynthetically fixed organic carbon into the soil consisting of a wide variety of compounds such as sugars, organic acids, and primary and secondary metabolites . Together with mucilage and border cells , root exudates provide a major source of nutrients for the rhizosphere microbiome . Root exudation is regulated under genetic control as well as in response to environmental conditions in the soil such as nutrient limitations or increase in toxicity . Exudate patterns are also recognized as one of the strongest drivers shaping the rhizosphere microbiome . As a central player in the rhizosphere ecosystem, it is imperative to understand root exudation patterns to unravel subsequent impacts to the surrounding soil and microbial community. Improvements in analytical instrumentation have made it possible to move from targeted to untargeted explorations with mass spectrometry to create root exudate fingerprints in its entire complexity . Regardless, the impact of such techniques relies partly on our exudate sampling techniques.

Detection of exudates in real-time is difficult due to rapid bio-transformation and sorption to the soil matrix. As such, common collection methods rely on root washing in hydroponic systems to overcome complications in the soil matrix and preserve native exudation profiles. However, a comparison between a soil-based collection method and hydroponic methods showed varied responses particularly in amino acid exudation although the underlying cause was not elucidated . It is possible that the differing growth conditions between hydroponics and soil,greenhouse pot which include differences in gas concentrations, mechanical impedance and microbial spatial composition, can elicit differing root exudation responses to the same environmental stimuli. Rhizoboxes offer the advantage of localized sampling in soil using sorption media such as paper and membrane filters, compound specific ion exchange binding resin or micro-suction cups placed closed to root zones of interest to collect exudates . Moreover, in a rhizobox fitted at the bottom with a porous rootimpenetrable membrane, a root mat is allowed to be formed which is then further transferred onto a collection compartment . The collection compartment containing soil could then be cut into thin slices parallel to the membrane to represent differing distances from the rhizosphere . While this approach can be used to investigate exudate release and sorption under soil conditions, the root mat growth generalizes exudate production in terms of the whole root system and occludes spatial exudation patterns. In a hybrid set up by Oburger et al. , the rhizobox is transplanted to a second specialized rhizobox for continued vertical root growth. This specialized rhizobox consists of a nylon membrane close to the transparent side to restrict root growth into the soil except for root hairs . This creates a vertical flat root mat onto which localized exudate samples can be collected. A comparison of this novel set up to conventional collection methods showed that amino acid exudation rates were most varied among the different methods , further highlighting the need for specialized chambers. Nonetheless, successful implementation of these chambers is still limited to fast-growing plants which can form active root mats. The high density of root mats could also lead to unnatural root exudate levels and an overestimation of rhizosphere effects. In addition, care has to be given to the choice of membrane as selective sorption of certain root exudates onto the membrane may also occur . Free-living nematodes are ubiquitous in the soil. They are beneficial to the plants by playing a role in nutrient cycling and in defense against insects and microbial infections through signaling interactions with the roots . Conversely, infections by parasitic nematodes in the roots increase the plant’s susceptibility to stress and other pathogenic bacteria, fungi, and viruses creating major losses in crop productivity . With an impending rise in nematode infections due to climate change, understanding nematode behavior and interactions in the rhizosphere becomes important to develop appropriate bio-control methods to ensure long term food security .

Traditional nematode studies are performed in petri dishes with agar or culture media . However, these substrates do not accurately emulate the physical textures and heterogeneity of soil and create homogenous solute and temperature gradients which could impact nematode behavior and interactions with the roots . Indeed, nematode motility speed and dispersal decreased in substrates more closely mimicking sand . On the other hand, studying nematode behavior in the soil is a difficult endeavor as its near-transparent body and small size makes it almost indistinguishable from soil particles. Cross-sectioning and staining infected roots make it possible for nematode visualization but they are destructive and provide only static snapshots of cellular changes or nematode behavior during infections . On the other hand, microscopy rhizosphere chambers provide non-invasive detection and observation of nematode activity in the rhizosphere . The roots in these chambers grow between a glass slide and a nylon membrane . The membrane restricts movement of roots except root hairs into the soil while the transparent glass enables microscopy of the roots at high resolution . Coupled with fluorescently stained nematodes, microscopy rhizosphere chambers allowed for non-destructive in situ observations of nematode infection in its host species over the entire life of the parasite . Nonetheless, staining nematodes is an additional challenge as nematode cuticles are impermeable to stains . This can, however, be alleviated by using advanced imaging technologies which eliminates the need for staining. A recent study demonstrated live screening of nematode-root interactions in a transparent soil-like substrate through the use of label-free light sheet imaging termed Bio-speckle Selective Plane Illumination Microscopy coupled with Confocal Laser Scanning Microscopy . Using this set up, researchers were able to monitor roots for nematode activity at high resolution and suggest its possible use in rapid testing of chemical control agents against parasitic nematodes in soil-like conditions . Fungal communities in the rhizosphere are involved in the degradation of organic matter in the soil and subsequent nutrient turnover affecting plant health as well as the microbial community . Fungal biomass often reaches a third of total microbial biomass carbon and almost all terrestrial plants are able to form symbiotic associations with mycorrhizal fungi .

The resulting NOx and SO2 pollutants need to be removed and recovered for reuse by a flue gas cleanup system

We believe that ample water and nutrients, mixed with the short lived, annual lifestyle of H. incana, led these plants to produce greater above ground biomass as compared to naturalized, or wild, H. incana found at the field sites. Conversely, native E. fasciculatum specimens showed more below ground root material than that of the invasive species. This is due to the perennial habit of the native, where a taproot and established root system would be necessary for survival. Because perennials such as E. fascicultum do not respond as quickly to increased nutrient availability, the species would not develop the same amount of biomass as that of H. incana during the exposure period. Overall, we observed complex movements of tracer within the individual PLS systems which may explain why we computed substantially different N deposition rates using sub-components of the modules than we computed with the module-average approach.Since Deployment 3 had aluminum foil installed 2 weeks after the exposure had begun, some nitrogen may have been lost to algal or microbial biofilms. In a few Hoagland Controls, there were also very small weeds that were also present. The small seedlings were included in the module calculations as they utilized module nitrogen during exposure, possibly adding a small source of error to deposition rates. Additionally, the prolonged time to senescence, 130 days, might have lowered the apparent N deposition rate as the winter season is not a time in which H. incana readily grows; instead H. incana sprouts with the last spring rains and grows primarily in the summer season. Because H. incana was grown out of season, we speculate that the plants were transpiring less water and therefore assimilating less gaseous N than plants exposed during the summer deployments , and therefore growing much slower. This is confirmed by the fact that Deployment 3 took 130 days for H. incana to reach senescence,growing raspberries in container but in Deployments 1 and 2 the species took approximately 70 days to senescence. I also noted that invasive treatments seemed to have smaller above ground plant structures than in previous deployments.

The AP 15N of below ground biomass had a relatively narrow compared to that of the above ground plant material . While this might be a physiological artifact, we speculate that nitrogen settling on the above ground plant surface directly from the atmosphere may have contributed to greater isotopic dilution and variability in the above ground biomass. Since below ground plant material is not exposed to direct nitrogen deposition, the roots did not experience the same depletion of the 15N tracer. In contrast, stomatal uptake of atmospheric N, and the subsequent allocation of this N to the root system, would be the major pathway in which root tissues would become depleted of 15N. The Control treatments, lacking a plant component but containing all other ITNI parts, resembled a passive nitrogen deposition collector, because there was no plant component in which to actively uptake gaseous nitrogen or deposition. Modules with plants had higher apparent N deposition because of active absorption of atmospheric N through leaf stomates and because of the larger surface area of plant canopies relative to the sand surface in the Control modules.In all deployments, and across all treatments, ITNI modules exhibited the following pattern of depositions rates using the different computation methods: Module Average> Plant> Above ground. This finding is explained by two factors. First, the plant is more isotopically enriched than the liquid and sand components of the ITNI modules so that the portion of Equation 1.3 in parentheses was lower when computed using only the plant than when it was computed using the module average; this smaller number was then multiplied by Ns to yield a smaller apparent N deposition. Secondly, the Ns value for the plant and the above ground plant are lower than the Ns for the entire module, further decreasing the value of N deposition in Equation 1.3. Thus our hope that the PLS would reach an internal isotopic equilibrium so that selecting only plant tissue for ITNI calculation could result in accurate N deposition failed. The high levels of tracer in the plant occurred because of early exponential growth when 15N tracer was abundant in the liquid reservoir. As the Deployment continued, the plant remained isotopically enriched compared to the other components of the module. The sand and liquid reservoirs, because of their small size, experienced higher levels of isotope dilution. This leaves the plant more enriched as the exposure continues as the plant does not appear to exude the 15N-labelled material back into the liquid and sand after it has been allocated to plant tissues.

Therefore, the different computational methods of Plant and Above ground are not helpful in determining the nitrogen deposition experienced by the modules. Module Averages are the only way to compute nitrogen deposition to ITNI modules. Module Average nitrogen deposition rates were greatest in Deployment 2, compared to Deployments 1 and 3, perhaps due to improved nitrogen recovery at harvest. As a consequence of calculating nitrogen deposition rate via the module average ITNI method, the rate is dependent on nitrogen recovery as represented by Ns. As Ns decreases, the nitrogen deposition rate experienced by the module also decreases, therefore underestimating true nitrogen deposition to the module over the exposure period. Since Deployments 1 and 3 lacked a foil barrier to deter algal/microbial growth in the module during the exponential growth of the plant, they recovered less nitrogen at harvest as a result. He et al., 2010, stated that plant detrital material was neglected in their ITNI measurements. In contrast, I included plant detritus during the harvest of the plants. Though the plant detritus was not actively taking up gaseous nitrogen, it derived from the ITNI plant and still experienced dry deposition to surfaces and therefore was included in the sampling for the respective modules. Plant detritus was most likely a conundrum for He et al. as the agricultural species that they utilized had plant organs that senesced during exposure. This senescence led to the volatilization of NH3, however our modules were harvested as soon as the plants senescenced, therefore reducing this nitrogen loss. In the case of E. fasciculatum treatments, there was no plant detritus to include, further supporting our suggestion that perennials, instead of agricultural or annual species, should be used as ITNI study specimens. Extrapolation methods were introduced by Russow and Bohme 2005 in which the plant density of the module was modified to match the field density of the same species. To correct for this in our own study, Bromus rubens, Hirschfeldia incana, and Eriogonum fasciculatum were sown in the ITNI modules at field density or very close to that of field density when sown a single seedling to a single module . Therefore, only the exposed sand surface was necessary for extrapolating ITNI calculations to the hectare level. Similarly to He et al. 2010, our study also experienced lower nitrogen deposition rates for species grown outside of their traditional growing season. He et al. Contributed this finding to less active uptake of gaseous nitrogen as compared to normal growing conditions. However, they found that despite this, the ITNI method produced higher deposition rates than traditional methods and concluded that this excess nitrogen deposition was active uptake by the plant.

According to the National Atmospheric Deposition Program, total nitrogen deposition for our study area ranged from 12 kg ha-1 yr -1 to 18- >20 kg ha-1 yr -1 . When extrapolated to an entire year, the ITNI method estimated total deposition to be approximately 38 ha-1 yr-1 , also exceeding NADP’s measurements. Since our study site was not dominated by wet deposition,raspberry container size as was He et al.’s, we attributed this excess deposition to the active uptake of gaseous nitrogen by the plant and improvements upon the shortcomings in dry deposition measurements in the region . Future ITNI experiments in arid and semi-arid regions should utilize a single or a very few, representative short-lived perennial species. We make this suggestion based on the considerable variability in biomass among individual specimens in the annual invasive treatments. If a short-lived perennial was used instead of an annual, we suspect there would be less influence from early senescence and less influence from a life history that promotes quick growth. Annual life history traits can increase the chance of biomass loss due to seeding events, flowering, pollen release, etc. By working with a perennial plant, ITNI operators can still grow a plant with enough aerial biomass to actively uptake nitrogen, but the plant is less likely to senesce or seed during the exposure period. Additionally, we suggest picking one, or just a few representative species, for the ITNI measurements across regions. Interspecies differences in life history, physiology, and aerial plant parts would interfere with a direct comparison across a region. However, if a single species were utilized across all habitats in question, spatial patterns in N deposition would be easier to detect. We also suggest that ITNI modules contain the same improvements as I have noted, such as the addition of a mechanism to prevent herbivory bird visitation and covering the modules to prevent light from entering the liquid reservoir to deter algal/microbial growth in the PLS system. Life support systems are what make human travel a possibility. In long range space travels, such as the travel to Mars, life support cannot depend upon storage alone, it requires a fully regenerative system as well, i.e. waste must be reclaimed for reuse. Steam reformation, supercritical water oxidation, electrochemical oxidation, and incineration are a few of the solid waste reclamation technologies that are being developed and tested for use in space travel. Currently though, it seems that incineration might be the best choice among the previously mentioned, in providing a fully regenerative system. Through rapid conversion, incineration of the inedible parts of wastes and crops produces carbon dioxide, water, and minerals. Incineration is already the most thoroughly developed technology for use in a terrestrial environment. However, with the use of incineration in a closed environment, there is the eventual buildup of pollutants that are emitted in the process. Important things to consider when developing a flue gas clean up technology for use in long range space travels are safety, energy requirements, sustainability, and doable under a micro-gravity condition.

Due to the sensitivity and restrictions of space missions, a flue gas clean up system lacking in any of these considerations can be hazardous and could potentially compromise the missions. Technologies requiring things such as expendables or the use of catalysts are unsuitable for space missions due to the loss of valuable resources and the possibility of catalyst poisoning thus limiting the life-span of a catalyst. Also, due to the micro-gravity, it is difficult to use wet processes that handle liquids, such as spray absorbers. Consequently, even though there are numerous flue gas clean up technologies developed , taking into consideration the limitation each provides, the number of reliable and applicable systems seem to be dwindling. Commercial activated carbon, made mostly from materials such as coconut shells and coal, has been studied for the adsorption and/or reduction of NOx and SO2 . In this paper, we study the use of the activated carbon prepared from hydroponic grown wheat straw and sweet potato stem for the control of air pollutants that are a result of incineration during space travel. Both wheat straw and sweet potato stalk are inedible biomass that can be continuously produced in the space vehicle. It was found that there is actually a minuscule amount of SO2 in the flue gas from the incineration of hydroponic biomass, and that most of the sulfur from the biomass ends up as sulfate in flyash. Since SO2 should have already reacted with the alkali metal, the technique entails the carbonization of the wheat straw and sweet potato stalk, resulting in an activated carbon for the adsorption of NOx and then a reduction of the adsorbed NOx by carbon to form N2. Since most NOx in flue gas from combustion is in the form of NO, and NO2 is readily adsorbed on the activated carbon, this paper concentrates on the removal of NO.

Activities of several vital antioxidant enzymes were determined after exposure to CECs

The continued observation of the formation of N4-acetylsulfamethoxazole, an acetyl conjugate, in the environment is of considerable interest because conjugates have the potential to maintain the biological activity of the parent compound . Further, because researchers traditionally only quantify parent compounds during environmental assessments, the formation and accumulation of conjugates implies that there may be an underestimation of environmental exposure to CECs such as pharmaceuticals and further incomplete environmental risk assessment of CECs . This is of particular concern for antibiotics, because of the rise of antimicrobial resistance . The major metabolite of methyl paraben, p-hydroxybenzoic acid, was observed in all soil samples, including the non-treated controls . This was likely due to the endogenous p-hydroxybenzoic acid in sphagnum peat . However, the concentration of p-hydroxybenzoic acid was higher in the spiked earthworm treatments than in the blank controls or non-earthworms chemical controls indicating that E. fetida was also capable of taking up and metabolizing methyl paraben and excreting of p-hydroxybenzoic acid into the soil. This was consistent with previous contact tests in which 70% of the initial methyl paraben was found to be metabolized to p-hydroxybenzoic acid and phenol within 48 h in E. fetida . The transformation products o-desmethylnaproxen and nordiazepam were not detected in earthworm tissues, but o-desmethylnaproxen was quantifiable in earthworm-CEC treated soils during the 21 d incubation , indicating active uptake, metabolism, and excretion. The quantification of the major metabolites for naproxen, sulfamethoxazole and methyl paraben, o-desmethylnaproxen, N4- acetylsulfamethoxazole, and p-hydroxybenzoic acid suggested a trend in the capabilities of E. fetida to take up, metabolize and excrete then transformation products of some CECs in the soil environment. Previous studies used radiolabeling and LC-FTMS analysis to assess potential metabolism of carbamazepine,blueberry plant pot diclofenac and fluoxetine in E. fetida but were unable to verify the presence of metabolites in earthworm tissues . Results from this and other studies indicated that metabolism may be chemical-specific.

To the best of knowledge, this was the first study to identify and quantify metabolites of these CECs in E. fetida dwelling in a soil. A significant increase in the activity of glutathione-S-transferase in the treatment samples over the controls was observed starting after 3 d into the incubation , and the GST activity continued to increase until the end of the 21 d incubation . This observation suggested that increased exposure time resulted in increased oxidative stress because glutathione is considered a critical antioxidant that acts to maintain redox homeostasis and signaling in cells . Further, GST is a crucial enzyme family for the detoxification of xenobiotics during Phase II metabolism . Thus, the observed increase in GST activity may indicate that there was a formation of additional Phase II metabolites. However, the detection of these potential metabolites was not attempted due to a lack of authentic standards. High GST activity was also observed at 0 h for both the controls and treated samples. However, this increase in activity is likely due to the initial stress of the earthworm being transferred into the test media, and the effect dissipated within the first day of exposure. No significant difference in catalase activity was observed between the treatment and controls until the end of the exposure period . At the 21 d time point a significant increase was seen in the treatment samples , indicating that extended exposure to CECs likely resulted in increased production of hydrogen peroxide in earthworm tissue . However, an increase in the CAT activity was also found in the control at 0 h. The increase in CAT activity was, again, likely due to the initial stress of the earthworms being transferred to different environmental conditions and the difference dissipated within 24 h. A significant increase in superoxide dismutase was observed at 1 d and 3 d . However, no significant differences were observed between the treatment and controls after 3 d . This trend was in accordance with SOD has the first line of defense against reactive oxygen species . SOD acts to catalyze the superoxide radical into oxygen molecules or hydrogen peroxide . As an increase in CAT was observed at the later time point it was likely that SOD activity increased initially, resulting in an increased production of hydrogen peroxide, which was then detoxified by CAT. Previous studies examining the biochemical effects of CEC exposure in earthworms showed somewhat similar trends.

For example, a study exploring the biochemical and genetic toxicity of triclosan in E. fetida showed a dose-dependent hormesis effect over time for both CAT and GST activity, with increasing activity being observed after a 2 d exposure at low doses and an inhibition of enzyme activity being observed after 14 d at high doses. Further, similar studies considering oxidative stress in E. fetida exposed to herbicides showed an increase in enzyme activities at lower concentrations and a suppression of enzyme activities at high concentrations . Thus, it is likely that the lower, environmentally relevant, concentrations of CECs used in this study resulted in the observed increase in enzyme activities while these concentrations were not high enough to cause an inhibition in enzyme activity. Currently we are experiencing a series of global trends that are creating unique challenges for the future of sustainable development. These trends include shifting precipitations patterns, rising temperatures, growing human populations, and rapid urbanization. In order to meet these challenges, traditionally under-utilized resources, such as treated wastewater and bio-solids, will have to be harnessed. These resources are derived from wastewater treatment plants and contain biologically active, pseudo-persistent, trace chemicals referred to as contaminants of emerging concern . Land application of TWW and bio-solids for agriculture and landscaping has the potential to introduce CECs into terrestrial ecosystems, from where they could accumulate, be metabolized and/or cause adverse effects in terrestrial organisms. This dissertation has described the ability of terrestrial plants and invertebrates to take up and metabolize CECs and highlighted the potential for these trace contaminants to induce biochemical changes in non-target terrestrial organisms. The findings of this project, overall conclusions, and recommendations for future work are summarized below. In arid and semi-arid areas, TWW reuse is becoming increasingly prevalent for agricultural irrigation. However, irrigation with TWW has the potential to introduce CECs including antibiotics into agroecosystems. One of the most commonly prescribed and environmentally relevant antibiotics is sulfamethoxazole. However, little is known about the fate of sulfamethoxazole in terrestrial plants. In this study, sulfamethoxazole was observed to be taken up and actively metabolized by Arabidopsis thaliana cells into six transformation products. The transformation products included oxidation of the amine group, producing Phase I metabolites, which was followed by conjugations with glutathione, glucuronic acid and leucine, producing Phase II metabolites.

Phase III metabolism was assessed by determining the mass balance of 14C-sulfamethoxazole in A. thaliana cells and cucumber seedlings. Non-extractable 14C-sulfamethoxazole increased over time in both A. thaliana cells and cucumber seedlings, indicating that Phase III metabolism significantly contributed to the fate of sulfamethoxazole in A. thaliana cells and cucumbers. Further, in A. thaliana cells and cucumber seedlings, the mass balances were calculated to range from 80-120% and 80-94%, suggesting a minor role of mineralization. The results from this study highlighted the potential of terrestrial plants to transform pharmaceuticals, forming both bioactive Phase I metabolites and Phase II conjugates, and store them as in the form of bound residues as Phase III metabolism. Plant uptake of CECs from TWW reuse and bio-solid application has been documented in agroecosystems. Previous studies suggested that plants were capable of metabolizing CECs after uptake. However, these studies often reported different results even with the same CECs,plastic gardening pots likely due to the use of different plant species and/or different laboratory conditions. In this study, the metabolism of the benzodiazepine diazepam was explored in three different plant species, A. thaliana, cucumber , and radish . The plants were exposed to diazepam in laboratory under three different laboratory exposure conditions that included a 6 d cell culture, an acute /high concentration hydroponic cultivation, and a chronic /low concentration hydroponic cultivation. 14C-Diazepam was incubated concurrently with non-labeled diazepam to determine the fractions of extractable and non-extractable radioactivity to quantify Phase III metabolism. Diazepam was taken up and metabolized in all plant species under the different exposure conditions. A. thaliana cells actively transformed diazepam into temazepam and nordiazepam via Phase I metabolism. This metabolism mimicked human metabolism, as temazepam and nordiazepam are the minor and major metabolites, respectively, formed during human metabolism of diazepam. Intriguingly, both of these metabolites are bioactive and prescribed pharmaceuticals in their own right, alluding to a potential for increased risk from consumption not considered in previous studies. The fraction of non-extractable residue increased over the 6 d incubation, indicating extensive Phase III metabolism over time in A. thaliana cells. In cucumber and radish seedlings, a similar Phase I metabolism pattern was observed, with nordiazepam being the most prevalent metabolite at the end of the 7 d and 28 d cultivations. However, significant differences in phase III metabolism were observed between the radish and cucumber plants. For example, after the acute exposure, diazepam mass balance was 99.3% for cucumber seedlings but only 58.1% for radish seedlings, indicating increased mineralization in the radish system. Diazepam induced changes in the regulation of glycosyltransferase activity in both cucumber and radish seedlings, indicating the formation of Phase II metabolites. The results from this study showed that exposure conditions and plant species can influence the metabolism of diazepam, and formation of bio-active transformation intermediates and different phases of metabolism should be considered in order to achieve a comprehensive understanding of risks of CECs in agroecosystems.

Exposure of terrestrial invertebrates to CECs will likely increase with increasing TWW reuse and bio-solid application. However, currently there is limited information on the fate and effects of CECs in terrestrial organisms. In this study, the earthworm E. fetida was exposed to three pharmaceuticals, i.e., sulfamethoxazole, diazepam, and naproxen, and one preservative, i.e., methyl paraben, for 21 d in an artificial soil. Methyl paraben did not accumulate in the earthworm tissue, likely due to its rapid degradation in the soil. The other CECs showed an accumulation in earthworm tissues from the soil/soil porewater. The presence of E. fetida did not significantly affect the adsorption of these CECs to the soil. The presence of primary metabolites in the treated soil suggested that E. fetida were capable of actively metabolizing the three pharmaceuticals and excreting the metabolites. However, the metabolism was chemical-specific, and only N4- acetylsulfamethoxazole was detected in earthworm tissues. Exposure to the four CECs also resulted in the up-regulation of several antioxidant enzymes, including glutathione-S-transferase, superoxide dismutase, and catalase, and an increase in malondialdehyde, indicating oxidative stress in the exposed E. fetida. Results from this study highlighted the need to consider the role of, and effects on terrestrial invertebrates when understanding risks of CECs in agroecosystems. Our findings illuminate the complexity of the interactions between contaminants of emerging concern and terrestrial organisms. The dissertation highlights the ability of terrestrial organisms to take up and transform CECs through metabolism, which results in both bio-activation and detoxification of the target contaminants. This project also demonstrates the ability of CECs to alter the biochemistry of the studied terrestrial organisms by changing the regulation of enzymes associated with oxidative stress and metabolism. The use of cell cultivations, hydroponic studies, and artificial soil allowed us to examine the metabolism and effects of CECs in terrestrial organisms with limited confounding factors. However, it is highly likely that similar studies conducted in soils may show low rates of uptake and different patterns in metabolism. Our research suggests that scientifically sound understanding of fate of, and risks from, CECs in the environment cannot solely rely on the assessment of the parent compound and/or only consider the potential for human exposure to CECs. One must also consider the potential for the formation of metabolites and the consequences of exposure to all non-target organisms in order to better understand the fate and risks of CECs in terrestrial environments. The results have potential implications for policy makers and other stakeholders attempting to assess the risks for the land application of treated wastewater and bio-solids.

Carbamazepine has been oftenreported to be taken up by plants in both field and laboratory settings

Arabidopsis thaliana, on the other hand, produced acyl-glutamatyl-diclofenac as the major Phase II metabolite via direct conjugation . Direct conjugation of naproxen and ibuprofen with glutamic acid and glutamine was also observed in Arabidopsis thaliana plants . The metabolism of acetaminophen has also been studied in multiple plant systems, including horseradish hairy root cultures and Indian mustard . In these studies, direct glucuronisation, glucosidation, and sulfation were observed along with the formation of a reactive metabolite N-acetyl-pbenzoquinoneimine . Taken together these studies have highlighted the ability of plants to uptake and transform NSAIDs. Several classes of psychiatric pharmaceuticals have been detected in TWW and bio-solids including antidepressants, mood stabilizers, and antianxiety agents . Of these compounds, carbamazepine has been likely considered in probably the most in the agroenvironment due to its stability during wastewater treatment and in the environment . In hydroponic systems, carbamazepine has been shown to accumulate in both roots and shoots of multiple plant species, including lettuce, spinach, cucumber, and peppers . Cucumber was found to readily translocate carbamazepine when cultivated in hydroponic systems . However, a high rate of translocation was not observed in cabbage plants cultivated in hydroponic systems . In greenhouse studies, carbamazepine was reported to be taken up by cucumbers and ryegrass grown in soils irrigated with TWW and urine . In addition, Shenker et al., reported that uptake into cucumbers was negatively correlated with soil organic matter content. In fields irrigated with TWW, trace levels of carbamazepine was found to accumulate in different parts of various vegetables . Carbamazepine was also reported to transfer to humans after consumption of contaminated vegetables . The metabolism of carbamazepine in plants has also been investigated . In carrot cell cultures five phase I metabolites of carbamazepine were observed to form over 22 d . Further, 10,11-epoxycarbamazepine and 10,11-dihydroxycarbamazepine have been reported in carrots and sweet potatoes grown in fields irrigated with CEC-spiked TWW . Fluoxetine is an antidepressant prescribed for both human and animal consumption ,blackberry container resulting in fluoxetine being commonly detected in environmental samples .

In hydroponic cultivations fluoxetine was taken up by cauliflower and accumulated in the stems and leaves . In a greenhouse study exploring plant uptake of fluoxetine from soils irrigated with TWW and amended with bio-solids fluoxetine accumulated in the roots , but, it was not translocated to the leaves . In addition, fluoxetine displayed an opposite uptake pattern to that for carbamazepine, and showed a greater accumulation in plants grown in bio-solid-amended soils as opposed to soil irrigated with TWW . Benzodiazepines, are one of the most prescribed classes of pharmaceuticals . Of these, diazepam is among the most commonly detected pharmaceuticals in TWW, with concentration ranging from ng L-1 to low µg L-1 . Benzodiazepines have been shown to be taken up and accumulate in tissues of plants grown in treated hydroponic solutions or soils . In hydroponic solutions, diazepam has been observed to accumulate in both the leaves and roots of lettuce, spinach, cucumber, and pepper with BCF of 10-100 ]. Further, in a greenhouse study exploring the uptake of seven benzodiazepines , both silverbeets and radish crops took up and accumulated all seven benzodiazepines from the treated-soil . Oxazepam was found to have the highest accumulation in both plants, with concentrations up to 14.2 µg g-1 in silverbeets and 5 µg g-1 in radishes . However, the fate of these pharmaceuticals in the agro-environment is still relatively unexplored, even though their physicochemical properties indicate a high potential for uptake by plants .A multitude of antimicrobials and preservatives are used in health and grooming products, collectively known as personal care products . Personal care products have garnered increased scientific attention due to their presence in surface waters and concerns that some of these antimicrobials and preservatives may be endocrine disruptors . Of these, triclocarban and triclosan have been amongst the best studied compounds in the terrestrial environment due to their ubiquitous occurrence in bio-solids and relative stability in soils after bio-solid application . Triclocarban and triclosan have been reported to be taken up by several crop species from hydroponic solutions. For example, after exposure to an aqueous solution mixture of triclocarban and triclosan 11 different food crops, cucumber, tomato, cabbage, okra , pepper , potato , beet, onion , broccoli, celery , and asparagus , were capable of taking up both compounds. However, translocation from roots to the aerial tissue was ≤1.9% for triclocarban and ≤ 3.7% for triclosan after 1 month of exposure . Similarly, Wu et al. found triclocarban and triclosan to have a translocation factor < 0.01 in four vegetables cultivated in a hydroponic solution with two initial exposure concentrations . In a greenhouse study, triclocarban and triclosan were taken up in radish, carrot, and soybeans from bio-solid-amended soils and, the greatest concentration was observed in the carrot root after 45 d of treatment and decreased thereafter .

However, in a three-year field study in which soils were amended with bio-solids in accordance with Ontario providence agricultural practices, the concentration of triclosan and triclocarban in the plant tissues was relatively steady and low . Plants have also been shown to metabolize triclosan, forming 33 metabolites in horseradish cell cultures with the majority being phase II conjugates . Further, one transformation product of the triclosan, methyl-triclosan, has been widely detected in environmental samples and is known to have greater toxicity than the parent compound . Parabens are common preservatives used in cosmetics, and among the most commonly detected CECs in TWW and bio-solid. Parabens are of concern due to their endocrine disrupting potential . Parabens have been widely detected in surface waters and sediments . However, knowledge of their behavior, uptake, and transformation in terrestrial systems is comparatively limited. Methyl paraben was unstable in soil after application of bio-solids, with the maximum concentration of 14.1 µg kg-1 reached after 5 h and decreasing to < 1 µg kg-1 after 35 d . In a bio-solid amended field, methyl paraben was the lone paraben detected in the bio-solids but was not quantifiable in tomatoes, sweet corn, carrot and potatoes . The above studies highlight the potential for CECs to enter the terrestrial environment, accumulate in plant tissues, and undergo transformations in plants. However, the wide variations in plant uptake and translocation rates under different soil and environmental conditions are currently not well understood and warrant further investigation. Further, it must be noted that the majority of currently published studies have focused on many of the same 20 or so CECs and explored their uptake in mostly the same plant species . There are over 1500 pharmaceutical compounds, alone, currently in circulation . Further, many of the current models have been shown to overestimate the concentration of CECs in plant tissues . In addition, no models have been able to take into account plant metabolism when determining the concentration and risk of CECs in terrestrial plants. More research is needed on a wider swath of CECs with different physicochemical properties in a wider range of plants to improve risk assessment. Transformation of CECs in the environment, including through plant metabolism also needs to be further investigated to better understand their fate and risks in the terrestrial environment. Antibiotic exposure in plants has been widely studied due to previously observed phenotypic toxicity. Several studies showed decreases in root length and changes in shoot development of various plants exposed to several different classes of antibiotics including sulfamides, fluoroquinolones, and penicillins .

Most of these studies were conducted at antibiotic concentrations greater than those of environmental relevance and/or utilized artificial or hydroponic growth media. For instance, shoot and root growth of pinto beans grown in a nutrient solution spiked with two antibiotics, chlortetracycline and oxytetracycline, significantly decreased in a dose-dependent manner . Enrofloxacin,planting blueberries in a pot a fluoroquinolone, induced hormetic and toxic effects on post-germination growth in lettuce, cucumber, radish and barley plants at concentrations ranging from 0.005 to 50 mg L-1 in laboratory conditions . Seed germination has also been studied as a potential biological end-point to assess toxicity to antibiotic exposure . The exposure effects on seed germination vary considerably by plant species and exposure chemical. In filter paper tests, sweet oat , rice and cucumber seeds were negatively impacted when the seeds were exposed to aqueous solutions of increasing concentrations of six antibiotics, i.e., chlortetracycline, tetracycline, tylosin, sulfamethoxazole, sulfamethazine, and trimethoprim . The EC10 and EC50 for seed germination were, however, significantly different depending on the antibiotic and the plant species. Rice seeds exposed to sulfamethoxazole were the most sensitive with an EC10 of 0.1 mg L-1 but tylosin had an EC10 > 500 mg L.-1 On the other hand, cucumber seeds exposed to sulfamethoxazole had an EC10 > 300 mg L-1 but an EC10 of 0.17 mg L-1 for chlortetracycline . Exposure to antibiotics can also change plant nutrient and chemical compositions. For example, irrigation with water spiked with sulfamethoxazole and trimethoprim increased production in carbohydrate and soluble solid contents in tomatoes as compared to the plants irrigated with untreated water . The mechanisms driving the phytotoxicity of antibiotics have also been explored. Antibiotics can be directly toxic to or indirectly affect plants. Indirect adverse effects can arise from antibiotic exposure that detrimentally affects mycorrhizal fungi, a vital plant-microbe interaction . Direct toxicity can result when antibiotics interfere with plant hormones or chemical synthesis pathways, or damage chloroplasts, etc. For example, sulfamethoxazole was shown to directly disrupt the folate synthesis pathway in plants by blocking the action of dihydropteroate synthase . Tetracyclines was shown to interrupt mitochondrial proteostasis and damage plant chloroplasts . Interactions with plant hormones may also play a role in the observed phenotypic phytotoxicity. Erythromycin and tetracycline can promote the production of abscisic acid in plants . Abscisic acid, a stress hormone, is crucial for plant responses to drought, salinity, heavy metals, among other stressors , but antibiotic-induced production of this hormone can cause premature leaf and fruit detachment and inhibit seed germination. Plants, depending upon species, can also detoxify antibiotics through reactions with phase II metabolic enzymes . However, studies so far have shown significant variations among plant species. For example, the antibiotic chlortetracycline was detoxified by glutathione conjugation via glutathione-Stransferase in maize , but glutathione-S-transferase did not efficiently catalyze the conjugation in pinto beans . These detoxification reactions, likely produce a series of conjugated metabolites that have yet to be characterized. Understanding the extent of such conjugation is crucial for estimating the total antibiotic uptake, accumulation, and translocation of antibiotics in plants as the formation of conjugates may mask the total concentration, even though some of these conjugates may retain biological activity . Several widely used NSAIDs, such as ibuprofen, acetaminophen, and diclofenac are amongst the most studied pharmaceuticals in the environment. Studies have shown that NSAIDs can induce toxicity to plants . Phytotoxicity, however, is often plant species and NSAID specific. For example, ibuprofen has been shown to inhibited root elongation in Sorghum bicolor at high concentrations, with EC50 of 232.64 mg L-1 . However, in seed germination tests exposure to a hydroponic solution containing 1 mg L-1 ibuprofen, along with other fenamic acid class NSAIDs, increased the length of the primary root in lettuce but had no effect on radish . In the same study, diclofenac was observed to decrease the root-to-shoot ratio in radish seedlings cultivated in a sand/spiked-nutrient solution , but did not significantly affect the seed germination. However, protein content was not affected in maize cultivated in soils irrigated twice with different concentrations of acetaminophen but grain yields and seed germination were negatively impacted in a dose dependent-manner . Plants can metabolize and detoxify NSAIDs. For example, plants were found to detoxify acetaminophen by conjugation with glutathione followed by conversion to cysteine and acetylcysteine conjugates . Similarly, diclofenac was found to be converted to glucose conjugates in barley and horseradish and glutamic acid conjugates in Arabidopsis thaliana . Arabidopsis thaliana cell cultures can detoxify ibuprofen via conjugation with sugars and amino acids .As mentioned above, pharmaceuticals used to treat psychiatric disorders are another group of frequently detected pharmaceuticals in environmental samples, particularly the anticonvulsant carbamazepine .

Post structural theories like Actor-Network Theory move beyond the material to include the symbolic lives of commodities

Despite the extensive and growing literature on local and alternative food networks , this form of inquiry, which consists of “following the thing,” has not been extended to local commodities, including those produced through urban agriculture. Unlike global commodities, the products of urban agriculture are often equated with accountability and transparency and do not receive the same kind of critical scrutiny. We challenge this notion which conflates local with ethical by arguing that local food products, like global commodities, have complex symbolic and material lives that mask social relations. Their commodity circuits are shaped by socio-natural relationships involving people, places, things and forces that produce value both discursively and materially. This research builds on the commodity chain concept by implementing the sort of multi-locale ethnography employed by Cook to examine the local commodity circuits and micro-geographies of urban agriculture in San Diego County. In recent years, urban agriculture has seen a surge of interest in cities throughout the United States. This growing curiosity has been accompanied by increasing diversity in the networks of human and non-human actors enrolled in urban agriculture. For instance, the introduction of new production methods – namely, soilless hydroponic, aquaponic, and aeroponic growing – has increased the heterogeneity of urban agriculture networks in cities. This type of diversification, in particular, is the focus of this paper. Soilless and soil-based urban agriculture networks embody different, although sometimes overlapping, urban political economies and political ecologies . Further, the food commodities they produce are entangled in unique, locally articulated networks of human and non-human actors that materially and discursively shape the way food is planted, grown, harvested, marketed, desired, and consumed in the city. Inspired by Cook and Actor-Network Theory , we juxtapose vignettes from various nodes in the commodity circuits of soil-based and soilless urban agriculture products to better understand the place-based, socio-natural relationships that scaffold different urban agriculture commodities in San Diego County. Our contribution lies primarily in the comparative approach we adopt to study the networks underlying and shaping the activities of three urban growing sites in San Diego: Coastal Roots Farm, Solutions Farm,large plastic pots for plants and Mount Hope Community Garden, chosen based on their growing practices, discursive similarities and dissimilarities, and unique socio-spatial settings .

Rather than focusing on a single food item, such as a papaya, we consider the output of urban agriculture more broadly – whether it is a head of hydroponic lettuce or a radish pulled from the soil. Vignettes related to these three enterprises are the result of mixed method research that combines interview, media, US Census , and participant observation data. Thirty-four semi-structured interviews and participant observation were conducted between 2016 and 2018 at multiple sites in the local urban agriculture networks of the three case sites. The interviews were approximately an hour in length and covered institutional histories, actors’ personal motivations for participating in urban agriculture, their growing practices, their perceptions of the local food environment, and the struggles and barriers they perceive to urban agriculture. These data were analyzed using exploratory spatial data analysis , which allowed us to examine the socio-economic landscapes that are the setting for these actor-networks, and multi-locale ethnographic analysis, which included emergent coding in Dedoose online coding software . When coding the interviews, we paid particular attention to the race-, class-, and gender-based power dynamics that accompany different urban agriculture commodities as they travel from place to place gaining meaning and value. Combining and analyzing this data was necessary for examining the “people, connections, associations, and relationships across space” that influence justice narratives and practices. The comparative focus we take is a response to popular claims that soilless growing is incompatible with justice and calls for more reflexive, nuanced understandings of justice . The concept of local commodity circuits provides an innovative approach to analyze the power relations underlying various forms of urban agriculture and shaping their capacity to promote food justice. Finally, this research illustrates the practicality of a post-capitalist approach to justice that acknowledges incremental, but still important, steps towards building more just food systems in the absence of structural change. This theory builds on from the authors’ concept of “diverse economies” which recognizes “each individual economic transaction and practice as a possible site of struggle and ethical decision-making” and rejects a priori judgments that classify certain economic practices as “good or bad” . This position, we argue, provides a fruitful avenue for examining the placed, context-dependent justice practices that unfold in the “here and now” . Especially important is its ability to recognize everyday actions that can “support conditions for positive social and economic transformation” .

This weaves productively with the everyday, nuanced justice advocated by Goodman, Dupuis and Goodman in their reflexive theory of justice. Indeed, Chatterton and Pickerill note the need for “detailed empirical accounts of the messy, gritty and real everyday rhythms as activists envision, negotiate, build and enact life beyond the capitalist status quo in the everyday” . This research seeks to answer this call by examining the multiple openings for justice found throughout local urban agriculture commodity circuits. Commodity circuits are scaffolded by ‘geographical knowledges’– peoples’ understandings of specific places . These knowledges and/or imaginaries include the settings, biographies, and origins and are “fragmentary, multiple, contradictory, inconsistent and, often, downright hypocritical” . The concept of geographical imaginations builds on Marxism’s commodity fetishism, which recognizes commodities as more than physical – “they are both things and relations” that have social and geographic lives and trajectories that are hidden behind their exchange value .Here, commodities are hybrid actants, as much social as they are natural, that exist in networks held together by their relations . The idea of ‘actants’ is unique to Actor-Network Theory. Latour notes, “An actant can literally be anything provided it is granted to be the source of action” , recognizing the importance of things, which lack the motivations typically associated with human actors, in driving action . Agency, as result, is less about intentional actions, and more about associations or network . In this research, we focus on stakeholders and organizations and refer to them as ‘actors’ because they have motivations and particular agendas that drive their action. We do not intend to simplify or ignore the role of actants such as narratives, growing materials, permits, and more that “authorize, allow, afford, encourage,permit, suggest, influence, block, render possible, forbid, and so on” action . Agency is a “distributed effect” of the associations between these things and actors in Actor-Network Theory . Examining these associations “allows us to explain the mechanism of power and organization in society and to understand how different things … come to be, how they endure over time, or how they fail” . However, critics of Actor-Network Theory note that agency is not evenly distributed and that this question of power differentials is missing from the theory. In fact, “some actants ‘marshall’ the power of others and, in doing so,plant pots with drainage limit the latter’s agency” . This gap, we argue, is remedied by intersecting Actor-Network Theory with commodity circuit analysis in which power relations are a central characteristic of networks.

Geographies of food undoubtedly lend themselves to the use of Actor-Network Theory , although researchers have questioned the transformative potential of research that describing lived experiences and associations without explicitly engaging larger structures such as the political economy. Goss argues that this ‘cultural turn’ “risk[s] throwing out the babies with the bathwater: rejecting a caricature of commodity fetishism they lose a concept that provides insight into the relationship between the material and symbolic” . However, in response, Cook argues that the theory exists “between the lines” and exploring the everyday associations that underlie commodities does inspires empathy and political transformation . Despite their disagreement, the two vantage points have much to offer one another. We agree that if we, as researchers, are to be agents of change and inspire effective, political action, we must engage and embed audiences in the lives of ‘others’ to inspire empathy and challenge faulty geographical imaginaries. However, we must be more than story-tellers hoping that the pieces come together in the minds of our readers – we must use theory to articulate the connections that we hope audiences would find ‘between the lines’. This research seeks to do just that in its examination of local, urban agriculture commodity circuits. This research uses Actor-Network Theory to unravel the geographical imaginations that structure the people, places, things, and forces – the “dots” –in our networks. Seeing the dots as relational, hybrid, and situated allows us to untie anterior narratives around the socialness and/or naturalness of actants in our networks and focus instead on relations and connections as they relate to food justice. We do attempt to make sense of the connections for readers; however, we do not see this as creating a ‘critical knowledge’ for consumption as Cook and Crang have described it. Instead, we see it as handing our readers a map of the theoretical trails we have identified that they may follow or stray from as they examine and build their own understandings of these networks. This theoretical map is built from a series of vignettes presented side by side that allow readers to make connections and develop their own critical understandings as they “follow the thing” before we input our own critical understandings. This research does not end with these pages, but is a continuing collaborative effort between the actors and actants outlined in its vignettes, its readers, and ourselves. Cool, humid, bright. The greenhouse at Solutions Farms vibrates with slow, continuous activity.

Dave, a retired marine whose curiosity for the science of aquaponics led him to Solutions, reminds me not to take photographs of the workers – men and women from seemingly all walks of life – as they tend numerous rows of white, plastic trays overflowing with green and purple lettuces. The workers are participants in Solutions for Change’s program which seeks to break the cycle of homelessness in families throughout San Diego County. The program focuses on combining skills, knowledge, and resources to participants including “transformational” housing, health services, counseling, life skills like financial literacy, and job training. Get up, suit up, show up. The unofficial motto of the program stated by each team member I interview at Solutions Farms. Dots of red embellish the lettuces’ soft leaves like ornaments. Step closer and the dots come to life. Lady bugs crawling slowly across the leaves in search of aphids – small, pesky insects that feed on the lettuces’ sap and, ultimately, the farm’s profits. The fish – all male tilapia – live in 2,000-liter tanks in the aquaculture room next door. Warm, humid, dark. Dave conducts this orchestra of people, plants, fish, insects, fungus, bacteria, minerals, nutrients, moisture, and machinery. There’s more chemistry and biology and physics and engineering than you can shake a stick at 2 . He was a volunteer at the farm until their systems specialist put in his two weeks. An amalgam of people, places, objects, and forces shape and structure the local commodity circuits of soilless and soil-based urban agriculture described in the vignettes above. This research sought to connect the dots between these vignettes in order to “lift the veil” and uncover the social relations that underlie these often taken for granted circuits. We did so by combining commodity circuit analysis and Actor-Network Theory to examine and compare the socio-natural relationships that comprise the placed networks that structure the commodity circuits and influence their abilities to enact justice. This practice illustrates the nuanced nature of justice as it unfolds across urban agriculture commodity circuits and provides evidence of the relationships that create openings for justice to be enacted and/or co-opted by actors. In addition to examining the connections within and between the vignettes, we created a network diagram that encapsulates the people, places, and institutions enrolled in the separate urban agriculture actor-networks that span the three commodity circuits. The diagram illustrates the flows of knowledge, capital, labor, food, and other resources between actors.

The growing diversity of urban agriculture calls for research that accounts for its increasing complexity

The primary goal of this paper is to understand whether there is a connection between the growing practices organizations and businesses use and the themes present on websites, especially those associated with justice. This paper quantitatively grounds further discussion of the discursive realities of urban agriculture in the second paper, “Thinking and doing justice: urban agriculture in San Diego County.” Using three case studies chosen based on their online discursive representations , socio-spatial settings, and growing characteristics, I examine how local urban agriculture organizations, including soilless and soil-based, define and practice justice. This paper takes a reflexive approach to justice that moves away from “politics of perfection” and is embedded in spatial justice and a progressive sense of place that is “open and receptive to diversity and plurality” . Specifically, I assess the role of distribution, participation, and recognition in justice narratives and practices, paying special attention to the socio-spatial settings they are embedded in locally. Analysis centers around the role of land, labor, and capital—all of which are used in urban agriculture in various degrees and forms. Using a spatial perspective that acknowledges the importance of place and context, I explore the role of these three factors in producing opportunities and barriers for the three organizations to achieve justice, highlighting disparities in access, ownership, and management among them. Building on these case studies, the final paper, “Connecting the dots: local urban agriculture commodity circuits,” in collaboration with Dr. Pascale Joassart-Marcelli, use multi-locale ethnographic analysis to explore the complexities and nuances of justice across the three case sites’ entire commodity circuits. Here, we examine the complex symbolic and material lives of the urban agriculture commodities at these sites and the unique,square plant pots locally articulated networks of human and non-human actors that support them. These networks embody different, but often overlapping, urban political economies and political ecologies that materially and discursively shape food production, distribution, and consumption.

We juxtapose vignettes from various nodes along each case’s commodity circuit to understand the place-based socio-natural relationships, including those related to class and race, that scaffold urban agriculture commodities and invite readers to “connect the dots.” Together, the three papers present a thorough account of the idiosyncrasies of justice in the growing, and increasingly diverse, urban food movement in San Diego County. They acknowledge, but ultimately abandon divisive narratives that make a priori assumptions regarding the connection between growing method and justice and instead unravel the question of how different forms of urban agriculture contribute to justice. As will become clear in the coming chapters, justice is more complicated than an abstract concept or measurable outcome – it is a process that is constantly unfolding within and across space.Urban agriculture has a rich history in the United States, evolving from a 20th century strategy for self-sufficiency to a radical and alternative approach to food production in the 1960s and 70s . Today, urban agriculture is a highly-commoditized feature of the urban landscape and represents a growing sector of the green economy . It is also more diverse than ever – traditional, soil-based practices like community gardening and farming on vacant, urban lots are now accompanied by small-scale, technologically-advanced, soilless forms of food production like hydroponics and aquaponics that enable food to be grown on rooftops, in greenhouses and abandoned buildings, and in mobile shipping containers. These physical distinctions are also accompanied by interrelated variances in “scope, scale, type of access and for whom, participants, and goals” . For instance, the participants undoubtedly influence the narratives and goals of an urban agriculture project, whether it be environmental sustainability ; human health and well-being ; distributive justice and economic autonomy ; challenging historical legacies of privilege and marginalization ; and/or participation in the new food economy . Recently, researchers of urban agriculture have begun paying attention to actors’ motivations and the narratives underlying them . However, this literature focuses almost solely on actors operating in the traditional networks of urban agriculture practice , paying little attention to recent and innovative approaches to urban agriculture that incorporate technology.

This research provides an inclusive account of the narratives, specifically online web page content, of urban agriculture sites and organizations in San Diego County – a county with a rich agricultural tradition that possesses both soil-based and soilless forms of UA. We use a novel, computer-mediated method that reveals hidden trends and avoids unproductive researcher biases. The result is a map of discursive relationships that transcends what we call politics of technology in which the narratives, and ultimately goals and motivations, of urban agriculture sites are taken for granted based on their growing methods. This politics of technology, which classifies certain forms of growing as either ‘good’ or ‘bad’ based upon their use of technology, is misleading. Instead, we argue that there is nothing inherently good or bad about urban farming methods. To support this claim, in this chapter, I examine the motivations and goals that are highlighted in the narratives presented on the websites of San Diego’s main urban agriculture organizations. The primary focus here is the ways organizations represent themselves and their work to the general public, including volunteers, policy makers, and potential funders. In subsequent chapters, I will turn my attention to the practices of these organizations in an attempt to draw connections between discourses and on-the-ground activities. This means more inclusive research that recognizes the many forms of urban agriculture, including new soilless configurations. For the purpose of this research, we define soilless urban agriculture as urban food production in greenhouses and in/on buildings that use hydroponic, aquaponic, or aeroponic technology. This definition expands the idea of “ZFarming” – referring to farming on zero acres including “rooftop gardens, rooftop greenhouses, indoor farms, and other building-related forms” – by focusing less on the location of urban agriculture and more on the production process. It excludes vertical and rooftop farms that do not incorporate hydroponics, aquaponics, or aeroponics and avoids vague monikers like ‘innovative’ or ‘high-tech’ . The physical descriptors associated with soil-based and soilless urban agriculture differ in the literature .

Using the term ‘soilless’ allows us to untangle our classification from those already established in the urban agriculture literature and draw attention to actors, technologies, and spaces commonly missing in definitions of urban agriculture. Soilless urban agriculture is an emergent feature of the urban agriculture landscape throughout the Global North; however, it is still in an “early innovation phase” . Little scholarly literature exists on soilless urban agriculture save for a few examples on stakeholder perceptions , descriptions of practices and novelties , and assessments of environmental and economic impacts . What research does exist tends to conflate it with entrepreneurialism . Rooftop agriculture is gaining recognition for its community and social justice benefits ; however, growing food on rooftops represents only a small aspect of technological innovation in urban agriculture. Urban agriculture is also practiced in greenhouses, warehouses, and shipping containers with or without the use of soil. Further, soil-based rooftop gardens may not carry the same stigmatization as those that use soilless technologies. Recently, researchers have examined the contributions that aquaponics can make to urban food sovereignty in Milwaukee and Melbourne ; however, this type of research is largely lacking. Here, we attempt to correct the direction of the current research agenda. Just as the seminal critique by Born and Purcell challenged the politics of scale that privilege local food production as inherently better without critical inquiry into actors’ agendas, we challenge the politics of technology in urban agriculture that privilege certain production methods as ‘inherently better’ without examining actors’ narratives and practices. Researchers have examined politics of technology in the context of the design of information technology, exploring the construction of ontological differences between “technology” and “human work” . Latour has also grappled with ethical arguments around technology,plastic pots for planting arguing that it is how we engage with technology that tips the moral scales. We ultimately build on Born and Purcell , arguing that there is nothing inherently superior about any given urban growing process and confusing the means by which food is grown in the urban setting with the ends that growing food in cities aims to achieve is fallible. The use of advanced technology in urban agriculture requires a reflexive, critical examination regarding the diversity of participants, narratives, and practices in urban agriculture. This research is preceded by a growing body of literature that examines the motivations of actors involved in urban agriculture in cities throughout the Global North . Recent research on urban agriculture organizations and businesses throughout Canada and the United States provides an interesting national context, identifying a series of motivational frames based on survey responses including Entrepreneurial, Sustainable Development, Educational, Eco-Centric, DIY Secessionist, and Radical frames . This research reveals some interesting patterns, but unfortunately does not include technologically-advanced forms of growing. This investigation of motivations links productively to an analysis of the topics underlying urban agriculture narratives. Indeed, narratives around health, sustainability, justices, and more, often are driven by and drive motivations; however, as researchers note, examining advertised narratives and stated motivations is not a substitute for examining practices – see discussion of justice by Cadieux and Slocum . To that effect, this research is but a step in the process of understanding urban agriculture in San Diego County. Our research takes a different approach from its predecessors who have used both qualitative and mixed method research designs. Inspired by the ‘digital turn’ in Geography , we identify the narratives underlying urban agriculture using an innovative, computer-mediated quantitative method that combines natural language processing, dimensionality reduction, and data visualization.

This approach recognizes that “socio-techno-cultural” artefacts like website content create digital geographies linked to, but independent from, physical location. Here, Tobler’s first law of geography – “everything is related to everything else, but near things are more related than distant things” – is transposed to the digital world where all content produced by urban agriculture growers and organizations is related, but near things are more related discursively than distant things. We chose this approach for its ability to unveil hidden patterns in advertised content that may go unnoticed in other approaches such as surveys and interviews and avoid the politics of technology.The analytical methodology we pursue in this study relies on the delineation of ‘canonical knowledge structures’ representing common and generally accepted ideas about urban agriculture within the academic literature. To that end, we employed topic modelling, specifically latent Dirichlet allocation . This method is a popular choice for distilling themes from a collection of documents referred to as a corpus . A corpus may consist of any group of texts including peer-reviewed literature , grey literature, blog post , and social media posts like tweets . LDA identifies common word associations among the documents and performs statistical extraction of latent topics . In addition, a set of topic loadings is computed for each document . In effect, a “hidden structure” is thus inferred from the corpus by the algorithm. The granularity of the model, i.e. the number of topics, is a crucial consideration and input parameter, balancing model fit and interpretability . The topic model provides the top words and top phrases associated with each topic, which can be used to develop a descriptive label for each topic. To build our reference model, we first determined a source of “canonical” knowledge on urban agriculture. Suitable, recognized content on urban agriculture exists in many forms including scholarly literature, federal and state program information, planning documents, and nonprofit sector descriptions, among others. We chose to focus specifically on scholarly literature which gains canonical status through the peer-review and editorial process and represents the diversity of discourse around urban agriculture. Articles span diverse fields including ecology, geography, sociology, urban planning, chemistry, and engineering. Using the Web of Science database, we topic-searched journal articles containing noun phrases of ‘city’ and ‘urban’ in combination with the nouns ‘agriculture’ and ‘farm*1’ which returned 1,414 records including the article title, abstract, and keywords. We did not use a geographic criterion for our search. This search was performed on September 11, 2017. Still a relatively new subject in academic inquiry – the oldest item in the corpus dating back to 1959 – literature on urban agriculture has proliferated in recent years.

The field was organized in an RCBD with six blocks and four genotypes per block

The terminal 1 cm of the three seminal roots of each plant were collected at 6 and 16 DAG. Roots from 12 plants were pooled per replication to obtain sufficient RNA, and four pools were used as replications for each time point/ genotype combination. RNA samples were extracted using the Spectrum Plant Total RNA Kit . Messenger RNA was purified from total RNA using poly-T oligo attached magnetic beads. After fragmentation, the first-strand cDNA was synthesized using random hexamer primers, followed by the second strand cDNA synthesis using dTTP for a non-directional library. The library for transcriptome sequencing was ready after end repair, Atailing, adapter ligation, size selection, amplification, and purification. The library was checked with Qubit and real-time PCR for quantification and bioanalyzer for size distribution detection. The quantified libraries were pooled and sequenced on Illumina platforms. The clustering of the index-coded samples was performed according to the manufacturer’s instructions . After cluster generation, the library preparations were sequenced on an Illumina platform and paired-end reads were generated. The number of reads per sample and different quality and mapping statistics are described in source data of Fig. 6. Reads were mapped to the Chinese Spring Genome RefSeq v1.0 combined with the 1RS arm from cultivar Aikang58, allowing a maximum of 1 SNP. Reads were mapped using the splicing aware STAR aligner from the Lexogen pipeline. Reads mapping to more than one location were distributed equally among the identical targets. Expression values were calculated using the trimmed mean of M-values normalization method. The sequence of the 1RS.1BL translocation in AK58 is available only as a preprint and no final gene names have been published,round plastic pot so we provide a table with the different names and genome coordinates to facilitate future cross-reference.

Approximately 750 million tons of wheat are produced worldwide every year , but further increases are required to feed a growing human population. One understudied area that can contribute to these yield increases is the role of different root architectures on wheat adaptation to different soils. Although some progress has been made in the understanding of root development and architecture in Arabidopsis , this knowledge is lacking in grass species . There have been some examples of phenotypic selection of root architecture in breeding programs , but those methods are laborious and can be accelerated by a better understanding of the genes controlling wheat root architecture. Rye , a close relative of wheat, is more tolerant to water shortages than wheat, and has been reported to have a more robust root system. The translocation of the short arm of rye chromosome one to wheat chromosome 1B contributes to above ground biomass and better performance under drought stress . To address bread making quality problems associated with the 1RS.1BL translocation , a recombinant 1RS chromosome including two wheat 1BS chromosome segment introgressions was developed to eliminate the two rye regions associated with the bread-making quality problems . We introgressed the newly engineered chromosome into the spring wheat variety ‘Hahn’ and generated 1RS/1RSww near isogenic lines . Previous field trials showed that the Hahn 1RS lines had significantly higher yield and better canopy water status than the 1RSWW NILs in both well-watered and water-stressed environments, although the differences were larger in the latter . From a cross between Hahn-1RSWW and Hahn-1RS, we generated two additional NILs, one carrying the distal and the other the proximal wheat segment . The two NILs carrying the distal rye region showed significant improvements in grain yield and canopy water status compared to NILs carrying the distal wheat segment .

The 1RSxR NILs also showed higher carbon isotope discrimination and increased stomatal conductance, suggesting improved access to soil moisture relative to the 1RSxW NILs . In the winter of 2013, heavy rains waterlogged a UC Davis experimental field that affected the four 1RS NILs at the early tillering stage. Although the affected areas were irregular, the 1RSxR were less affected than the 1RSxW NILs. Based on this observation and previous results, we hypothesized that the 1RSxR lines might have a more extensive root system than the 1RSxW lines, which helped them tolerate both waterlogging in this experiment and water shortages in the previously published experiments . The first objective of this study was to characterize the effect of the wheat-rye polymorphism in the distal region of the 1RS.1BL translocation on root architecture in the field, and on plant biomass and grain yield under normal, excessive or reduced irrigation. After we observed that the lines with the distal wheat segment had shorter seminal roots than the lines with the distal rye segment in hydroponic conditions, we also decided to study the effect of these genotypes on seminal root growth rates, distribution of reactive oxygen species, and distribution of lateral roots. The implications of the observed differences in root development and architecture are discussed. In this study, we used four near isogenic lines that showed differences in grain yield in previous work . The recurrent common wheat parent of these NILs is the spring wheat cultivar ‘Hahn’ developed by the International Maize and Wheat Improvement Center . The Hahn cultivar carries the complete 1RS translocation from rye, and the three NILs differed from Hahn either in the presence of a distal interstitial segment of wheat chromatin , a proximal interstitial segment of wheat chromatin , or both . The interstitial wheat segments were introgressed from the common wheat cultivar ‘Pavon 76’ to eliminate the Sec-1 locus from 1RS and to incorporate the Glu-B3/Gli-B1 locus from 1BS into the 1RS chromosome to improve bread-making quality .

The source of this 1RS arm was the rye cultivar ‘Petkus’, and the resulting 1RS.1BL translocation became widely distributed in wheat breeding programs around the world . Controlled water logging experiments were conducted during the 2013-2014 and 2015-2016 growing seasons. An additional experiment was performed in 2014-2015 but it was not analyzed due to severe weed problems. The experiments were planted in November and harvested in June . The two water logging experiments were organized in a split-plot randomized complete block design with four blocks in 2014 and three blocks in 2016. Within each block, the main factor was irrigation treatment, and within each irrigation treatment – block combination, the Hahn 1RS, 1RSWW, 1RSRW, and 1RSWR genotypes were used as sub-plots. The average trait values of the 1RSxR and 1RSxW NILs were compared to determine the effect of the distal rye and wheat chromosome segments. In the 2014 field experiment, each block included two different irrigation regimes as main plots. The first treatment was based on plant needs and normal practices in California’s Sacramento Valley and is designated hereafter as normal irrigation. The second treatment, referred hereafter as water logging, consisted of artificial flooding twice a week starting in late January and ending in late March during the tillering stage, followed by normal irrigation. Water was applied via flood irrigation, and the soil profile remained saturated. While plants were not kept fully or partially submerged, there were persistent pools of water on the soil surface indicating a waterlogged environment. Each genotype was planted in three adjacent 1 m rows with 30.5 cm spacing between rows at a rate of 30 grains per row. Genotypes were separated by an empty row , and treatments were separated by a minimum of a border row, an irrigation levee, and another border row,round pot leaving in excess of three meters between experimental units of different treatments. Experimental units were replicated six times within each of the four blocks in an RCBD pattern and were used as sub-samples. At the end of the season, each set of three rows was harvested and grain yield was recorded. The average of the six sub-samples was used as a single data point in the statistical analysis. Canopy Spectral Reflectance measurements were taken for all sub-samples on two days . Sub-samples were averaged within days, and day averages were used as repeated measures. Canopy spectral reflectance measurements were taken with the “ASD HandHeld 2 Pro” spectrometer from Malvern Panalytical. Measurements were taken using a “scanning” method in which 50 measurements were taken on a single plot and averaged to give a single reflectance spectrum. From these measurements, differences in biomass between genotypes were estimated using the Normalized Difference Vegetation Index , which was calculated using the formula /, where R = reflectance at the specified wavelength. In the 2016 field experiment, each block included three irrigation treatments. The first treatment was grown under normal irrigation as described above.

The water logging treatment included flood irrigations three times a week, from the beginning of February to the end of February, followed by normal irrigation. The terminal drought treatment was grown under normal irrigation conditions until late March , and no additional irrigations after that point. Within each block–treatment combination, each genotype was machine sown in 2.23 m2 plots , which were combine-harvested at maturity. In 2016, CSR measurements were taken as described above on March 24th , April 6th , April 13th and April 28th . Days were used as repeated measurements and were analyzed as sub-sub-plots in an RCBD split-split-plot design using conservative degrees of freedom for days and all their interactions . After the CSR measurements were completed, an irrigation pipe ruptured flooding several sections of the experiment on April 29th, resulting in increased variability in the final yield measurements. Flooding was irregular and inconsistent across blocks, with major effects on replications two and three of the drought treatment and replication two of the waterlogging treatment. The field experiment to estimate root length was conducted after a maize crop harvested in the summer of 2016.Plots were machine sown in 4.5 m2 plots in November 2016 and were grown under normal irrigation conditions. To obtain soil core samples at specific depths and avoid differential soil compaction, we excavated ~2 m deep trenches cutting perpendicular across the middle of plots including complete blocks one , three and six to expose the root system. We took horizontal soil core samples from the center of each block at 20 cm intervals using a thin-walled copper pipe . Core samples were taken from 20 to 140 cm in the first block and from 20 to 180 cm in blocks three and six after we discovered the presence of roots at 140 cm in block 1. Plants were at the tillering stage at the time of the root sampling.Soil core samples were washed using a hydro-pneumatic elutriation system from Gillison’s Variety Fabrications, Inc. . After washing and sorting white turgid roots from other organic matter and decayed roots of the previous maize crop , we suspended the roots in water and scanned them using an EPSON Expression 11000XL flatbed scanner. Scanned root images were analyzed using the WinRhizo software package. Measurements of dry root biomass are not reported because they were too variable due to small biomass, stray soil contaminants, and changes in ambient moisture. The 20 cm sampling point was not used because the large amount of root biomass and organic matter present in these samples made them difficult to clean and measure. Since all root measurements were performed using soil cores of identical volume we refer to these measures as densities . Differences in total root length, surface and volume density, average root diameter, and root tips and fork densities were analyzed using a split-plot design with genotypes as main plots and depth as subplot. This is a conservative statistical analysis because it reduces the df for genotype from 3 to 1. Therefore, we also compared the two same pairs of genotypes using statistical contrasts in an ANOVA including all four genotypes. To account for the inability to randomize depths, we used a conservative estimate of the df for subplots and for the interaction between subplot and main plot. Conservative df were calculated by dividing their df by the number of subplots. This strategy is similar to that used for repeated measures in time and does not affect comparisons among main plots , which are the main objective of this study. Homogeneity of variance and normality of the residuals was confirmed for all the individual ANOVAs performed at each depth for all parameters.

A change in this ratio from the control suggests a change in the overall health of a plant

At the end of the 7 d incubation, root growth of lettuce seedlings was found to increase with increasing rates of the CEC mixture with significant differences observed at the 2X, 10X, and 20X concentration . Compared to the control, root length was found to increase by 16 ± 3, 24 ± 6, and 32 ± 8 % at the 2X, 10X, and 20X CEC concentration levels, respectively. This was in contrast with studies that showed negative root length effects when plants were exposed to other CECs such as tetracyclines and sulfonamides . However, in those studies, high concentrations of a single CEC were generally considered. For example, Liu et al. observed inhibition of root growth in oats, rice, and cucumbers when the seedlings were exposed to oxytetracycline concentrations at 5-10 mg L-1 . Chemical mixtures may involve more complex interactions, where various chemicals may have different but related targets that can have an additive or nonadditive effect . This may be the reason for the observed stimulatory effect by the CEC mixtures at environmentally relevant concentrations in this study. It could also be the result of a biphasic response where a favorable biological response at low dose and inhibition at high dose is observed, a phenomenon known as hormesis . Primary root length after 7 d germination is indicative of the plant’s ability to establish itself and obtain nutrients during this critical period of development. The stimulatory effect on root length observed in response to the low-dose exposure of a mixture of CECs in this study suggested that a low-dose mixture may help the plant establish itself better and increase its ability to obtain water and nutrients during the beginning stages of growth. However,10 liter drainage collection pot it must be noted that only a small set of CECs were considered in this study, and a similar response may not necessarily occur for other CECs or for these CECs with a different species.

Roots, stems, and leaves each maintains their own dynamic balance in biomass that is indicative of the relative above-ground resources and below-ground resources . The root to shoot biomass ratio provides insight into the overall health of the plant. A lower root to shoot ratio suggests greater investment in above-ground tissues possibly due to interference with photosynthetic mechanisms or interference in root functioning, resulting in reduced nutrient uptake and therefore growth . A greater root to shoot ratio is typically influenced by below ground conditions, suggesting reduced water and nutrient availability. Although no significant differences in root to shoot ratio with respect to biomass during the 7 d study, a positive correlation between CEC treatment levels and root to shoot ratio was observed , suggesting a possible interference with nutrient or water uptake by the roots. This was in agreement with Carter et al. , who found that carbamazepine and verapamil exposure caused changes in sodium and calcium ion flow regulation in zucchini plants, demonstrating the influence of CECs on nutrient transport. Since toxicity can only be elicited when a chemical has reached its target site, we monitored bio-accumulation of the target CECs into various cucumber tissues. The starting concentrations and their dissipation in the nutrient solution after 3 d with and without plants are found in Table 6. The 20X CEC treatment was used because the higher concentrations facilitated qualitative evaluation of CEC bio-accumulation and translocation. Among the various cucumber tissues, only one flower sample per treatment was collected due to the limited growth duration and plant tissue. Samples of flowers had to be pooled from replicates for each treatment, and therefore some standard deviations could not be calculated for the CEC concentrations in flower samples. Concentrations of CECs in plant tissues increased with increasing concentrations in the hydroponic solution . All CECs except triclosan were detected in the roots .

The absence of triclosan in the root samples could be due to its relatively high quantification limit of triclosan , active metabolism , or suppressed uptake of triclosan in the presence of other CECs. Above-ground and below-ground biomass were measured for cucumber plants at the end of a longer-term exposure to the same CEC mixture in hydroponic solution at incremental levels. Biomass measurements are useful in measuring stress response, as deviations in growth from the control are indicative of the overall sum of response of the plant . Although there were no significant differences in the biomass among the different CEC levels, there appears to be a dose dependent response when change in biomass, expressed as the percentage difference relative to the control, was considered . At the 20X treatment, the relative percentage differences in the average below ground, above ground, and total biomass from the control were -51.2 ± 20.9, -26.3 ± 34.1, and -33.2 ± 41.7%, respectively . The greatest reduction in plant biomass occurred in the roots, and this finding was similar to Carter et al. who also observed a ~30% reduction in the below ground plant tissues of zucchini from the control when the plant was exposed to 10 mg kg-1 carbamazepine in soil. The observed reduction in above-ground biomass and total biomass along the dose-response curve suggested that there was not simply further investment in photosynthetic or aerial tissues due to interferences in photosynthetic mechanisms, but rather that multiple aspects of the plant were affected without ways to mitigate the stress . It was also possible that the roots could not support an increase in aerial tissues, the common stress mitigation mechanism, because the roots were also under stress and were unable to take up the necessary nutrients to promote growth.A hormone profile was analyzed to further understand the dose-response effect of chronic exposure to a mixture of CECs on cucumber plants . In this study, we focused on three phytohormones; auxin , jasmonic acid , and abscisic acid because of their critical roles in regulation of a plant’s development and stress-response. The auxin profile was characterized by a hormesis effect along the dose-response curve when the leaves and stems were considered . The solvent control did appear to have some stimulatory effect on auxin concentrations in the stems , but the change was not statistically significant . A 6-fold increase was observed in the stem auxin concentrations at the 1X CEC treatment level as compared to the control .

The trend, however, was followed by a gradual decrease to 2-fold the control at the 10X CEC treatment rate . The leaf auxin concentrations significantly increased at the 1X and 10X CEC treatment rates to 16 and 11-fold, respectively,10 liter drainage pot which was followed by a decrease at the 20X CEC treatment rate. A similar pattern in leaf auxin content was also observed by Carter et al. along a dose-response treatment of carbamazepine for zucchinis grown in soil. A similar pattern, however, was not visible for the auxin content in the roots or fruits at the end of 30 d cultivation in this study. Auxin is known to be involved in cell elongation and division of meristematic tissues. The observed increase of auxin inthe stems and leaves at CEC levels as low as the 1X treatment rate suggested that the stems and leaves were being signaled to grow in order to gain increased light exposure because of interferences with photosynthetic mechanisms, and/or decrease heat stress by allowing for more air flow. Jasmonates are phytohormones that are involved in flower development, fruiting, reproduction, and plant defense. No clear trends or significant differences were observed in JA levels in any of the plant tissues along the dose-response curve . This could be due to the time of sampling, as the plant was still in an early stage of development , when flowering and fruiting was not the primary focus of the plant. Instead, at this point in development, increasing photosynthetic tissues was likely of the upmost importance. ABA is a signaling hormone that communicates water stress to the plant. ABA levels were significantly elevated in the leaves with exposure to increasing levels of CECs and significantly decreased in the roots at environmentally relevant concentrations of the CEC mixture . ABA in the roots dropped from 56.5 ± 17.3 ng g-1 in the controls to 8.23= ± 9.5, 5.6 ± 2.2, and 11.8 ± 13.7 ng g-1 at the 1X, 10X, and 20X CEC treatment rates. Low ABA levels in the roots could indicate over-saturation by water at the root tips. In this study, we observed an approximate 20% decrease in root ABA levels when the plant was exposed to the CEC mixture at the 1X level as compared to the control, demonstrating that even exposure to CECs at low levels could significantly affect the homeostasis of this hormone. The decrease in the ABA levels coincided with visual symptoms of the roots, where the roots appeared to be over-saturated and less rigid structurally, which also resulted in a ‘shedding’ of some small roots into the hydroponic medium. In the leaves, ABA was found to increase significantly at the 1X, 10X, and 20X CEC treatment levels from the control 42.6 ± 12.8 ng g-1 . Elevated ABA levels can cause stomatal closure, thereby reducing transpiration in a plant’s efforts to conserve water . The increase of ABA in the leaves and its resulting effect on anti-transpiration and therefore decreased pulling force of nutrients to aerial tissues could be the reason for the reduction in above-ground biomass observed in this study. Antitranspiration activity may also impose an impediment on plant growth by limiting gas exchange and impairing the plant’s ability to adapt to additional stressors such as extreme temperatures . With stomatal closure, the plant’s ability to mitigate heat stress by transpiring is also impacted, threatening its survival. 2.3.5. Phytohormone response to multiple stressorsFollowing cultivation in CEC-containing nutrient solution, a subset of cucumber plants was exposed for 4 d to heat stress at temperatures up to 41 °C in a greenhouse, and the plants were then sampled for hormone analysis.

JA content was not significantly altered with the additional heat stress in the roots and stems . Although, a significant effect on the JA content in the leaves was not observed following any of the lower level CEC treatments, JA content in the 20X treatment was significantly increased from JA content in plants exposed to heat without CEC exposure . A consistent trend across CEC treatments was a decrease in the JA content in the leaves in response to heat stress.Jasmonates are important signaling molecules in plant defense, and therefore a decrease in JA content in leaves in response to heat stress across all CEC treatments has implications for plant survival when exposed to disease, wounding, or pathogens . Although heat-stress exposed plants did not have statistically significant changes in JA content, this decreased trend in the JA content in leaves exposed to excessive heat conflicts with a study where heat shock was found to result in an upregulation of JA pathway genes and its consequentially enhanced production in agarwood cells . This could be due to the type of heat exposure , the range of temperature exposure, or the difference at the cellular level . Auxin concentrations in the roots of the control treatments with heat stress were significantly elevated as compared to the 1X and 20X CEC treatments . This finding showed how different types of stress may have opposing effects on plant hormone levels. In the stems, heat stress resulted in a significant decrease in auxin concentrations in plants in the 1X CEC treatment as compared to the 1X CEC treatment without heat stress , however the 1X CEC treatment with the added heat stress was not statistically different from the control or the 20X CEC treatment. The role of auxins in cell division and elongation has recently been associated with being an adaptive growth response to high temperature tolerance as seedlings elongate to elevate photosynthetic and meristematic tissues away from the heat-absorbing soil, thereby allowing increased air circulation and cooling effects . Leaf auxin concentrations were not affected by heat stress . Between the control and 20X CEC treatments, heat stressed plants displayed only slightly elevated auxin contents from their respective CEC treatments without the additional heat exposure. ABA is integral to how plants mitigate heat stress.

Individual kernel mass was greatest under both ambient and elevated CO2 treatments

The germination paper was placed in a 400 mL beaker with approximately 75 mL of 10 mM CaSO4 solution, covered with a plastic bag and placed in an incubator for four days. Seedlings were transplanted into 20 L tubs filled with an aerated nutrient solution that contained 1 mM CaSO4, 1 mM K2HPO4, 1 mM KH2PO4, 2 mM MgSO4, and 0.2 g L−1 Fe-NaEDTA and micro-nutrients 2HPO4 as the N source, Epstein and Bloom, 2005. The nutrient solution was replaced weekly and an additional 0.2 mM of NO− 3 – or NH4 + − N was added midweek until harvest. The solution volume was maintained by daily addition of deionized water. Solution pH varied between 6.8 and 7.0 for both of the N forms, and the NH4 + and the NO− 3 solutions did not differ by more than 0.1 pH units. The plants were grown in controlled environment chambers set at 23/20˚C day/night at 60–70% relative humidity with a photo period of 15 h. The photosynthetic flux density was 375µmol m−2 s −1 at plant height. Plants were subjected to one of three CO2 concentrations: “sub-ambient” , “ambient” , and “elevated” . sub-ambient CO2 concentrations were maintained by passing air that entered the growth chamber through wet soda lime, a mixture of KOH, NaOH, and Ca2 that was replaced as needed. The elevated CO2 conditions were maintained in an environmental chamber equipped with non-dispersive infrared analyzers for CO2 and valves that added pure CO2 to the incoming air stream to hold the chamber concentration at 720 ppm. The wheat was grown until all above ground parts turned completely yellow. Plant matter was sorted into grain, chaff, shoots,growing strawberries vertically and roots and dried for 48 h at 55˚C. Data on kernel number , kernel mass, number of heads, kernels head−1 , and HI were collected prior to sample preparation for nutrient analysis.

A portion of the grain was analyzed for phytate using a modification of the method as described by Haug and Lantzsch . The remainder of the grain as well as the shoots and chaff was bulked into five repetitions per treatment and sent to the UC Davis Analytical Laboratory for nutrient analysis. The roots of plants for each CO2 × N treatment became entangled within the same tub; therefore, we were unable to separate the roots of the individual plants for analysis. Root data are thus presented as means for each treatment with no standard errors or confidence intervals. Data were analyzed using PROC MIXED . Nitrogen form and CO2 factors were treated as fixed independent variables. We used the Tukey–Kramer Honestly Significant Difference test for mean separation. Probabilities less than 0.05 were considered significant. Because some of the transformed variables did not meet the assumption of homogeneityof variances, but one-way ANOVAs met the ANOVA assumptions, we analyzed the results via one-way ANOVAs to gain some information on the interactions between CO2 and N form.We used a database derived from the United Nation’s Food and Agriculture Organization ’s national food balance sheets to estimate the average daily per capita dietary intake of zinc and phytate from 95 different food commodities in each of 176 countries. This database combines FAO data on per capita intake of food commodities with USDA data on the nutrient or phytate content of each of these commodities. More detailed discussion of the creation of this database for the International Zinc Collaborative Group may be found in Wuehler et al. . Using this database, we produced two datasheets: one containing per capita daily dietary intake of zinc from each food commodity for each country and another containing per capita phytate intake from each food commodity for each country. To calculate total dietary zinc and total dietary phytate per country, we summed across the rows of all food commodities for each respective country. To determine the proportion of a population at risk for zinc deficiency from a hypothetical least developed country , we first calculated TDP and TDZ values for a set of 44 countries defined by the United Nations as being least developed. We took the mean TDP and TDZ values for these countries to represent a hypothetical “less developed country.” To calculate the bio-available zinc portion we used the Miller equation .

Mean TDZ and TDP values were converted to mg mmol−1 and put into the Miller equation to compute the average per capita TAZ in our hypothetical LDC. The variables TDZ, TDP, and TAZ are described above, and Amax, KP, and KR are constants as described in Miller et al. . We made an assumption that our hypothetical LDC receives half of its phytate and half of its zinc from wheat, which is roughly consistent with many of the LDCs in the FAO database. We analyzed the effect of elevated carbon dioxide levels on TDP, TDZ, and TAZ concentrations in a hypothetical LDC population for both NH4 + and NO− 3 -supplied wheat. To calculate a new TAZ for wheat grown under elevated CO2 conditions, we first calculated the percent change in TAZ from ambient to elevated levels for wheat receiving NH4 + or NO− 3 . This computed percent change was then applied to half of the hypothetical TDZ and TDP; meanwhile, the other half of the hypothetical TDZ and TDP remained unmodified. Thus, the total new TDP and TDZ is the sum of the unmodified and modified portions. These new TDP and TDZ values for both NH4 + and NO− 3 -supplied wheat were then put into the Miller equation to compute new hypothetical TAZ values for an LDC. Differences and corresponding percent changes between the new TAZ values and the original TAZ value for a LDC were computed to determine the overall affect of elevated CO2 on TAZ in NH4 + and NO− 3 -supplied wheat for an average developing world population. TAZ, TDP, and TDZ concentrations can only be compared within a single N form across the CO2 concentrations due to methodological constraints of the model. Plants supplied NH4 + vs. NO− 3 nutrition reacted differently to CO2 enrichment . Plants supplied NH4 + differed across CO2 treatments for most of the yield and biomass measurements. The greatest values typically were found at ambient CO2 concentrations. Shoot, chaff, grain yield, number of heads, and KN were greatest at ambient CO2 levels. HI and kernels head−1 showed no change across CO2 treatments. In contrast, biomass and yield measures of NO− 3 -supplied plants did not differ among the three CO2 concentrations.

At sub-ambient CO2, differences between the NH4 + and NO− 3 treatments occurred in shoot biomass and three of the yield components: kernel mass, head number, and kernels head−1 . Ammonium-supplied plants had a larger number of heads while NO− 3 -supplied plants had greater shoot biomass, kernel mass, and kernels head−1 . At ambient CO2, NH4 + -supplied plants had a greater number of heads and greater chaff biomass. Plants supplied NO− 3 had a larger number of kernels head−1 . At elevated CO2, biomass and yield measures did not differ with N treatment. Phytate was relatively insensitive to CO2 concentration. Phytate concentrations were highest at sub-ambient CO2 for NH4 + -supplied plants . Sub-ambient CO2 also produced the lowest phytate concentrations in NO− 3 -supplied plants. NH4 + -supplied plants had greater phytate concentrations than NO− 3 -supplied plants at sub-ambient CO2,best vertical garden system but not at the other CO2 concentrations. Grain from plants grown under NH4 + nutrition had roughly 7, 18, and 8% higher bio-available Zn than NO− 3 -supplied plants at sub-ambient, ambient, and elevated CO2, respectively . Based on this phytate and bio-available Zn data, we modeled how a human population from a LDC would be affected by changes in atmospheric CO2 concentrations . The calculations were based on differences among CO2 concentrations; therefore, modeled TDZ, TDP, and TAZ values cannot be compared between NH4 + and NO− 3 -supplied grain. Grain from plants supplied the different N forms behaved differently as CO2 concentration increased. We found that under NH4 + supply, TAZ would increase 3.6% with the rise in CO2 from sub-ambient to ambient, and decrease 1.6% with the rise from ambient to elevated CO2 . Humans provided NO− 3 -supplied wheat would experience a decrease in TAZ of 3.5% going from sub-ambient to ambient, and an increase 5.6% from ambient to elevated CO2 . Ammonium-supplied plants generally showed a trend toward decreasing nutrient concentrations with increasing CO2 concentration while NO− 3 -supplied plants varied widely across CO2 treatments . The decrease in nutrient concentrations under NH4 + supply corresponded to an increase in root mass. Nitrate supplied plants tended to have their highest nutrient concentrations in the ambient and elevated CO2 treatments. Ammonium supplied plants had higher concentrations of Zn and Mn across all of the CO2 treatments, as well as higher total N and Fe at sub-ambient CO2. Nitrate-supplied plants typically had higher concentrations of the other nutrients at all CO2 concentrations.

The distribution of nutrients and micro-nutrients among plant parts followed similar patterns in both the NH4 + and NO− 3 – supplied plants, although the NH4 + -supplied plant distributions were slightly more variable . Allocations to root and grain usually were greatest at ambient CO2, and those to chaff and shoots at either sub-ambient or elevated CO2. Grain typically contained the largest proportion of total N, P, Zn, and Cu, although the organ with the largest percentage of Cu varied with CO2 treatment among NO− 3 -supplied plants. Plants at sub-ambient and elevated CO2 allocated more Cu to the grain, while those at ambient CO2 allocated more to the roots. In general shoots received the majority of K, S, B,Ca, and Mg for all N and CO2 treatments. Ammonium-supplied plants allocated slightly more Mn to the roots at sub-ambient CO2, but allocated increasing amounts to the shoots at the expense of the roots as CO2 concentration increased. In contrast, NO− 3 -supplied plants allocated most of the Mn to the shoots. Ammonium-supplied plants typically allocated more resources to the chaff while NO− 3 -supplied plants allocated a greater percentage of elements to the roots.No other study to our knowledge has examined the influence of N form on plant nutrient relations at three different atmospheric CO2 concentrations. Overall, N form affected growth, total plant nutrient contents, and nutrient distribution in senescing wheat shoots, grain, and roots. The influence of NH + 4 and NO− 3 on growth and nutrient status were so distinct that they should be treated as separate nutrients and not bundled into a general category of N nutrition. Wheat size and nutrition at senescence responded to CO2 concentration in a non-linear manner. As was previously shown , we found that plants supplied with NH4 + were more responsive to CO2 concentration than those supplied with NO− 3 . Although not explicitly addressed here because of the heterogeneity of variances, interactions between CO2 and N treatments likely existed for a number of the biomass and nutrient measures. Most nutrient concentrations were generally higher in NH4 + – supplied plants, with the exceptions of NO− 3 − N, Mg, B, and Mn, which were generally higher in NO− 3 -supplied plants. Phytate, which hinders human absorption of Zn and Fe , showed little variation at ambient and elevated CO2 between NH4 + and NO− 3 -supplied plants, which, in conjunction with the observed greater bio-available of Zn in NH + 4 -supplied plants, may have consequences for human nutrition. Distribution of nutrients to the shoots, roots, chaff, and grain in response to CO2 concentration and N form was also non-linear and varied by nutrient. The data support our hypothesis that NO− 3 -supplied plants would show a more limited biomass and yield enhancement with CO2 enrichment than NH4 + -supplied plants. Nevertheless, mean biomass and yield decreased from ambient to elevated CO2 in both NO− 3 – and NH4 + -supplied plants in contrast to biomass increases in prior work on wheat seedlings . NO− 3 – supplied plants allocated more biomass to roots and had larger root:shoot ratios than NH4 + -supplied plants regardless of CO2 concentrations as has been reported previously , but increased root mass at elevated CO2 concentration for NO− 3 -supplied plants reported previously were not observed here.

There is also a growing concern about the effects of their environmental transformation products

The annual exposure values ranged from 0.32 × 10-3 mg for BPA-lettuce to 2.14 × 10-2 mg for DCL-collards for an average, 70 kg individual residing in the United States. To place these amounts in context, the values were then converted to either medical dose or 17β-estradiol equivalents. Both DCL and NPX are commonly available non-steroidal anti-inflammatory pharmaceuticals. Based on typical doses and the observed plant concentrations, an average individual would consume the equivalent of much less than one dose of these medicines in a year due to consumption of leafy vegetables, representing a very minor exposure to these PPCPs. However, it should be noted that DCL has proven ecotoxicity and NPX has shown toxicity in mixture with other pharmaceuticals , so a simple estimation may not encompass all possible human health effects. Both BPA and NP are industrial products known to have endocrine disrupting activity. Bonefeld-Jørgensen et al. calculated the Relative Potency of these compounds as compared to 17β-estradiol , an endogenous estrogen hormone, at activating estrogenic receptors. In Table 4.3, the exposure values of BPA and NP were estimated as E2-equivalents by dividing by their Relative Potency . When the calculated E2-equivalents of BPA and NP are compared with the Lowest Observable Effect Concentration for E2 , it is obvious that the even the highest expected annual exposure to these compounds by consuming leafy vegetables would not reach the LOEC. This rough calculation suggests that consumption of vegetables would be unlikely to influence an individual’s overall endocrine activity,container vertical farming though caution should be used when considering risk to susceptible population groups.

Moreover, it must be noted that the use of hydroponic cultivation likely resulted in greater plant accumulation of these PPCP/EDCs, in relation to soil cultivation, due to the absence of chemical sorption to soil organic matter and minerals. This likelihood, when coupled with the fact that most of the 14C in plant tissues was in the non-extractable form, implies that the risk from actual plant accumulation of these PPCP/EDCs by leafy vegetables grown in uncontaminated fields irrigated with reclaimed water may be negligibly small. On the other hand, bio-solids have been shown to contain some PPCP/EDCs at much higher concentrations than treated wastewater and plant uptake from soil amended with bio-solids may pose an enhanced human exposure risk. Also, given that many PPCP/EDCs may be preferentially distributed in plant roots as compared to above-ground tissues , the potential risk may be significantly greater for root vegetables such as carrots, radishes, and onions. The occurrence of these and other PPCP/EDCs in leafy and root vegetables should be evaluated in the field under typical cultivation and management conditions.Population growth, urbanization, and climate change have created unprecedented stress on water resources. The reuse of treated wastewater from wastewater treatment plants is increasing by 15% each year to help meet water needs . As of 2006, about 3.6 × 109 cubic meters of treated wastewater were reused in the U.S. each year for purposes including agricultural and landscape irrigation . Regulations on wastewater reuse are mostly concerned with pathogen and heavy metal contamination . However, numerous studies have shown that a variety of trace organic contaminants are present in treated wastewater, including pharmaceutical and personal care products and endocrine disrupting chemicals . Some PPCP/EDCs have unintended biological effects on nontarget organisms at low concentrations .The beneficial reuse of treated wastewater for agricultural irrigation introduces PPCP/EDCs into the soil environment, where they may be taken up by plants and cause human exposure by ingestion .

While a number of studies have examined the uptake potential of PPCP/EDCs, most studies only considered a few compounds, making it difficult to discern the underlying mechanisms. On the other hand, plant uptake has been extensively investigated for many pesticides and herbicides . Studies show that systemic pesticides are passively taken up through the transpiration stream , and greater transpiration leads to increased accumulation of non-ionic compounds . Many PPCP/EDCs are ionizable compounds that may exist partially as ions at an environmentally relevant pH . The ionic state of a compound greatly affects the compound’s interactions with plants, such as adsorption on root tissue, interaction with the cell membrane, and sequestration into plant compartments . In a recent study, Wu et al. examined multiple PPCP/EDCs and observed a strong correlation between plant bio-concentration of a compound and its pH-adjusted octanol-water partition coefficient , but did not address transpiration effects. Herklotz et al. and Shenker et al. suggested that movement through transpiration-driven mass flow of water was likely an important route for the uptake of carbamazepine, and Carter et al. suggested that transpiration differences between radish and ryegrass contributed to their differential uptake of carbamazepine, diclofenac,fluoxetine, and propanolol. However, to date researchers have yet to quantitatively evaluate the dependence of plant accumulation of PPCP/EDCs on transpiration. In this study, we measured plant accumulation and translocation of 16 PPCP/EDCs, including neutral and ionizable compounds, in 3 plant species grown hydroponically in nutrient solution. Plants were grown in growth chambers with different environment regimes to impose two distinct transpiration patterns. Losses of nutrient solution through transpiration were monitored throughout the 21 d incubation and the levels of PPCP/EDCs in plant tissues were measured at the end of cultivation. The effect of transpiration on bioconcentration or translocation was statistically evaluated for anionic, cationic, and neutral PPCP/EDCs. Knowledge of the interplay between transpiration and plant uptake is useful for identifying types of PPCP/EDCs, as well as weather conditions, that may have a relatively high tendency for plant accumulation and pose potential human health risks.

Three plant species were included in this evaluation. ‘Champion II’ tomato seedlings were purchased from Armstrong Growers and ‘Nevada’ lettuce seedlings were purchased from Do-Right’s Plant Growers at 3 weeks post seeding through a local nursery. ‘Danvers 126’ carrot was started from seed in commercial potting soil and seedlings were used at 26 d post-seeding. Two growth chambers with open circulating air were used in this study. One chamber was programmed to simulate a cool and humid environment with a day time temperature of 17 °C, followed by a night time temperature of 15 °C, while the relative air humidity was kept at 80%. The other growth chamber was programmed to simulate a warm and dry environment with a day time temperature of 27 °C, a night time temperature of 20 °C, with humidity at 50%. The cool-humid and warm-dry environments were used to induce distinctively different plant transpiration patterns. Both chambers received irradiation from a mix of incandescent and fluorescent bulbs, which gradually ramped over 7 h each day to a maximum light intensity of 300 µmol/m2 -sec2 which was maintained for 2 h before decreasing to darkness for a total daily photoperiod of 16 h. Six days before the start of the incubation,hydroponic vertical garden plants were carefully removed from their growth media, rinsed with DI water, inserted through jar lids, fitted with the foam collars, and placed in 2 L glass jars filled with fresh nutrient solution, at one plant per jar. After the plants were transferred to the growth chambers, jars were attached to a small pump system to aerate the solution with ambient air. After 3 d, plants were transferred into clean jars of fresh nutrient solution to replenish nutrients and minimize microbial growth. After a total of 6 d of acclimation, 4 replicates of each plant species in each chamber were randomly selected and transferred into clean jars with 1900 mL of fresh nutrient solution that was amended with 5 mL of a working solution of PPCP/EDCs prepared in ultrapure water. The nominal concentration was 1 µg/L for each compound in the nutrient solution, a level at the higher end of concentration ranges found in treated wastewater effluents . The actual chemical concentration of each compound was measured with solid-phase extraction, as described below. Plants were grown for 21 d in the growth chambers. Every 1 to 3 d, based on the amount of solution transpired, all plants were transferred to clean jars containing fresh solution fortified with PPCP/EDCs. At each solution exchange, the masses of fresh and used solutions from each container were gravimetrically measured to determine the exact amount of solution transpired by each plant. The total transpired mass was defined as the cumulative mass of nutrient solution removed from a jar throughout the 21 d incubation. Evaporation from jars was negligible due to use of fitted lids. The pH in the nutrient solution was measured at that time with pH paper; which was later used to calculate the average log Dow of each compound . At 21 d, all plants were removed from their treatment jars, rinsed with DI water, and separated into different parts.

For lettuce and tomato, plants were divided into leaf, stem, and root tissues. For carrot, plant was separated into leaf and root. Plant tissues were weighed, placed in self-sealing plastic bags, and then stored at -70 °C before analysis. To characterize the depletion of PPCP/EDCs in the nutrient solutions between solution exchange, solution samples were analyzed for levels of PPCP/EDCs on day 8 and 10. On day 8, freshly prepared nutrient solutions were analyzed for the initial chemical concentrations of PPCP/EDCs. To determine the masses of PPCP/EDCs remaining in the solution after 2 d of plant growth, the used nutrient solution from each plant container on day 10 was analyzed. To estimate the potential removal of PPCP/EDCs not attributable to plant uptake, triplicate jars of fortified nutrient solution without plants were included in each growth chamber for 2 d and then similarly analyzed. Prior to analysis, nutrient solution from each container was weighed and mixed by shaking, from which a 275 mL sub-sample was removed. The solution sample was extracted according to a previously published method . Briefly, 100 µL of surrogate solution was added to each sample. A Supelco Visiprep DL solid phase extraction manifold with disposable liners and HLB cartridges were used for extraction. Cartridges were sequentially conditioned with 5 mL each of MTBE, methanol, and water, and samples were loaded at 5 mL/min under vacuum. Sample vessels were rinsed with 200 mL of ultrapure water, and the rinsate was also passed through the cartridge. Sample cartridges were dried with nitrogen gas and then eluted with 5 mL each of 90/10 MTBE/methanol and methanol. The eluent was evaporated under a gentle stream of nitrogen at 40 °C to a volume of 400 µL and then transferred to a 2 mL glass vial. The condensing vessel was rinsed twice with 300 µL of methanol and the rinsate was added to the sample vial to make the final volume to be 1.0 mL for analysis.The extraction of plant tissue samples followed a previously published method . In brief, plant samples were removed from the freezer and immediately placed in a freeze-drier . Samples were dried for 16 h, or to dryness,and then weighed. Each plant sample was then finely ground in a stainless steel coffee grinder. The grinder was cleaned between samples using soap, water, and acetone. A 0.20 g aliquot was placed in a 50 mL polypropylene centrifuge tube and spiked with 100 µL surrogate solution. Samples were sequentially extracted with 20 mL MTBE, and then 20 mL acetonitrile, by sonication in a Fisher Scientific FS110H ultrasonic water bath for 20 min followed by centrifugation at 3000 rpm. The combined supernatant from each extraction step was decanted into a 60 mL glass tube and evaporated at 40 °C under a gentle flow of nitrogen to a volume of 0.5 mL. The residue was re-dissolved in methanol and then mixed in 55 mL ultrapure water. The SPE cartridges were conditioned with 5 mL methanol and then 5 mL water. Samples were passed through cartridges at 5 mL/min under vacuum, and then sample tubes were rinsed with 30 mL of ultrapure water, which was also passed through the cartridge. Sample cartridges were dried with nitrogen gas and then eluted with 7 mL methanol. The eluent was evaporated under a gentle stream of nitrogen at 40 °C to a volume of 200 µL and then transferred to a 2 mL glass vial. The condensing vessel was rinsed twice with 150 µL of methanol and the rinsate was added to the sample in the vial to create a final volume of 0.5 mL.

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