Category Archives: Agriculture

CB has been deemed persistent in the environment but with a low potential for bioaccumulation and toxicity

Root exudation may also be altered after nanomaterial exposure.In addition, adsorption of nanomaterials to bacterial cell surfaces has been reported to disperse nanomaterial agglomerates.Such processes and other soil characteristics could cause temporal variations in CNM behavior within the natural soil environment, including differentially over the course of plant growth. The results of the CNM concentration-dependent agglomeration in aqueous soil extracts qualitatively explained the observed inverse dose–response trends, which deviate from typical sigmoidal dose–response relationships reported for toxicants that dissolve in soil water , but quantitative tests are not possible because of the complex soil characteristics and dynamic processes described above. In this study, with nondissolving but agglomerating CNMs, small amounts of CNMs in moist soil did not agglomerate but rather remained suspended in soil water where they were more bio-available and impactful to soil microbes and plant roots. With larger amounts of CNMs in moist soil, large agglomerates formed, which led to a sharp decrease in their bio-availability and observed impacts . Although the inverse dose–response patterns were mostly shared across CNMs, the relationships were linear for CB and fit a power function for MWCNTs . Differences in agglomeration and possibly differing toxicity mechanisms could explain the differing model fits. Our results demonstrate that not only the mass concentration and primary particle size but also the level of agglomeration may play critical roles in determining CNM effects on plants and their root symbioses in soils. In prior microbial toxicity and hydroponic phytotoxicity studies, it was recognized that nanomaterial effects would increase as nanomaterial size decreases but would decrease as nanomaterials agglomerate. For instance, antimicrobial activity was found to be higher for smaller versus larger graphene oxide sheets,while debundled, short,nft system and dispersed MWCNTs were demonstrated to have relatively higher bacterial cytotoxicity due to enhanced MWCNT–cell contact.Depicted as “nano darts”, individually dispersed single-walled carbon nanotubes were reported to induce more bacterial death than SWCNT aggregates, as dispersed SWCNTs directly damaged bacterial cell membranes.

In hydroponic studies, dispersed MWCNTs were found to have stronger effects on tomato plants than MWCNT agglomerates.Even when comparing among agglomerates, small MWCNT agglomerates exerted stronger impacts to Arabidopsis T87 cells than large agglomerates.Still, the dose–response relationship for unstudied low concentrations, which are, across the herein unstudied range of 0 to 0.1 mg kg−1, is uncertain. It is possible that the whole-plant N2 fixation potential decreased continuously with CB concentration until 0.1 mg kg−1 . Alternatively, there could be a threshold concentration somewhere between 0 and 0.1 mg kg−1, possibly close to the lowest studied dose , above which the inhibition of the whole-plant N2 fixation potential occurred but below which it did not . There is uncertainty in such untested low concentration regimes. Such uncertainty reinforces the challenges in extrapolating toxicological results from studies using only high nanomaterial concentrations to low concentration exposure scenarios, owing to influential effects of nanomaterial physicochemical structuring.We chose multi-walled carbon nanotubes and graphene nanoplatelets as two representative engineered CNMs, with industrial carbon black for comparison. CB has been commercialized for decades in the rubber and pigment manufacturing industries,with annual production of over 10 million metric tons.However, there is evidence that CB may have similar or higher toxic effects on soil bacterial communities and amphipods compared with other CNMs.Therefore, assessing whether CB affects soybean and N2 fixing symbioses and comparing how the effects differ from those of MWCNTs and GNPs are important from an environmental regulatory standpoint. MWCNTs and GNPs were purchased from Cheap Tubes Inc. ; carbon black was purchased from Dorsett & Jackson Inc. . Besides the manufacturer reported properties , CNMs were characterized by transmission electron microscopy , thermogravimetric analysis , and inductively coupled plasma optical emission spectroscopy for material morphology, thermal stability, overall purity, and metal composition, following previously reported methods.The CNMs were used as received without further purification.

Three concentrations of MWCNTs, GNPs, and CB were evaluated in this study. A sequential 10-fold dilution method accompanied by mechanical mixing was used to prepare homogenized soil and CNM mixtures as reported previously.The mixing was performed using a hand-held kitchen mixer, from the low to the high CNM concentration treatments, with the mixer cleaned between different CNMs to avoid contamination. The cleaning procedure followed guidelines recommended by the National Institute for Occupational Safety and Health for cleaning surfaces contaminated with carbon nanotubes.CNM dry powder was weighed and amended directly into soil in concentrations of 0.01, 10, and 100 g kg−1 . Each mixture was blended thoroughly using the mixer for at least 10 min. These CNM–soil stocks were then diluted ten times by the addition of unamended soil and mixing by the mixer similarly as above, resulting in concentrations of 0.001, 1, and 10 g kg−1. The dilution and mixing were repeated again to achieve the final CNM working concentrations of 0.1, 100, and 1000 mg kg−1. The CNM–soil mixtures were stored prior to planting.Bradyrhizobium japonicum USDA 110 was initially streaked from frozen stock glycerol onto solid modified arabinose gluconate medium24 with 1.8% agar in a Petri dish, then cultivated in the dark. Following incubation, several discrete colonies were dispersed into 4 mL of liquid MAG medium. An aliquot was inoculated into a 500 mL glass flask containing 100 mL of liquid MAG medium and incubated in the dark for 5 d until stationary growth phase. Aliquots of the culture were dispensed into centrifuge tubes and centrifuged , and the supernatant was discarded. Cell pellets were resuspended in a 1 M MgSO4 solution to an optical density at 600 nm of 1.0 to serve as the inoculum during seed planting. Soybean seeds were purchased from Park Seed Co. . Seeds were inoculated with B. japonicum following the method of Priester et al.Specifically, seeds were soaked in the B. japonicum inoculum for 10 min and deposited into rehydrated peat-filled seed starter pellets at 1/4-in. depth using forceps. An aliquot of the B. japonicum inoculum was dispensed into the pellet holes over the planted seed; the seed plus additional inoculum were then covered with a thin layer of the peat pellet substrate. The pellets were watered daily and incubated on a heating mat . Each planting pot was comprised of a 3 qt high density polyethylene container with bottom perforations, which was lined with polyethylene WeedBlock fabric at the bottom, and overlain by 400 g of washed gravel to allow water drainage.

A polyethylene bag punched with 40 evenly spaced 5 mm holes was placed over the gravel, and 2.3 kg of soil was weighed into each bag. Perforation of the bags allowed for water drainage, thereby preventing root rot within the soil-filled bags. Overall, there were 10 treatments, including three concentrations for each of CB, MWCNTs, and GNPs, plus a control soil without nanomaterial amendment. There were eight replicate pots per treatment. Ten days after seed sowing, 80 VC stage 59 seedlings were transplanted into potted soils. Prior to transplanting, the outside mesh of the starter pellets was removed carefully to minimally disturb the seedling roots. A central planting hole was formed in the soil, into which B. japonicum inoculum was dispensed. One seedling was inserted into the hole, and another aliquot of B. japonicum inoculum was dispensed onto the surface. Both inoculation steps were deemed necessary for adequate contact between B. japonicum and the soybean roots and thus effective inoculation. The filled transplanting hole was covered by a thin layer of soil, and the potted soil surface covered by a layer of WeedBlock fabric to minimize soil surface crusting and weed growth. A wooden support stake was inserted against the inside wall of each pot for later plant support by tying, as needed. After transplanting, the plants were grown for another 39 d to the R6 stage in the Schuyler Greenhouse at the University of California at Santa Barbara. The greenhouse climate was controlled using VersiSTEP automation under full sunlight. The indoor air temperature ranged from 15 to 34 °C,hydroponic gutter and the indoor photosynthetically active radiation fluctuated between 21 and 930 μmol m−2 s −1 from nighttime to daytime. Soil moisture sensors were inserted to a depth of 13 cm into the soil of seven pots to monitor soil volumetric water content, electrical conductivity, and temperature. Data were recorded at least twice daily using a ProCheck data display . Pots were watered to retain an average soil volumetric water content of 0.25 m3 m−3 .Midori Giant is a determinate soybean variety, which stops vegetative growth soon after flowering initiates.Also, N2 fixation will accelerate when plants initiate pod development. Therefore, plants were harvested at each of two stages: intermediate or final , aimed at capturing CNM effects on plant vegetative growth with early nodule formation, and then reproductive development with highest N2 fixation potential. Three replicate plants from each of the ten treatments were sacrificed at the intermediate harvest , and five replicates were sacrificed at the final harvest , when plants reached stage R6 .At harvest, plants were separated, above ground from below ground, by cutting the stem at the soil surface using a single edge razor blade. The above ground part was further divided into stem, leaves, and pods . Leaves and pods were counted and arranged according to their sizes, then photographed. Total leaf area and pod size were further quantified by analyzing the images using Adobe Photoshop software.Sub-samples of fresh leaves and pods were weighed and then stored for future analyses.

The remaining tissues were transferred to separate paper bags, then weighed before and after drying to determine wet and dry biomass plus gravimetric moisture content. The below ground plant parts were removed from the pot within the polyethylene bag surround. The soil in the bag was gently loosened from around the roots and nodules using a metal Scoopula , while minimizing root system disturbance. The relatively intact below ground parts, including roots and nodules, were rinsed in deionized water thoroughly to remove remaining attached soil, then air-dried. The nodules were carefully excised from the roots using a single edge razor blade and forceps as reported previously.Nodules were counted; sub-samples were weighed and refrigerated for later TEM analysis. The remaining nodules were weighed and then analyzed immediately for N2 fixation potential. Roots were dried and massed as above, to determine gravimetric moisture content and dry biomass. After N2 fixation potential measurements, nodules were also similarly dried and massed. After acquiring dry masses, all dried plant parts were archived for future analyses. Sub-samples of soil from each pot were collected and stored for future analyses. The N2 fixation potentials of root nodules were measured as nitrogenase activity by the acetylene reduction assay, according to standard methods with some modifications.Pure acetylene gas was generated by the reaction of calcium carbide and deionized water in a 1 L Erlenmeyer flask, with C2H2 collected into a 1 L Tedlar bag . Intact nodules that were freshly excised from cleaned plant roots were placed into a 60 mL syringe with a LuerLok Tip and incubated with 10% C2H2 . At 0, 15, 30, 45, and 60 min, 10 mL of the gas sample in the syringe was injected into an SRI 8610C gas chromatograph with a sample loop to measure the C2H2 reduction to ethylene over time. The GC was equipped with a flame ionization detector and a 3 ft × 1/8 in. silica gel packed column. Helium was used as the carrier gas at a pressure of 15 psi . Hydrogen gas and air were supplied for FID combustion at 25 and 250 mL min−1, respectively. The oven temperature was held constant . The C2H4 peak area and retention time were recorded using PeakSimple Chromatography Software . Chemically pure C2H4 gas was diluted by air and measured to establish a C2H4 standard curve . The C2H4 peak area values were converted to C2H4 concentrations against the standard curve and further to moles of C2H4 using the ideal gas law assuming ambient temperature and pressure. For each analysis, the moles of C2H4 produced were plotted over time, and the relationship was evaluated for linearity, then fitted by a linear regression model to calculate the C2H4 production rate. The N2 fixation potential was calculated as the C2H4 production rate normalized to the assayed dry nodule biomass.

Are Plastic Or Ceramic Pots Better For Plants

In the case of K+ sensing, we have shown here that not only the transporter proteins but also the components in the low-K+ response signaling pathways respond to K+ status by altering their protein abundance . In addition, the regulation of protein levels occurs at the post-translational level for all components, calling for future effort to identify the enzymes and regulators that connect nutrient availability to protein stability. In fact, our effort here indicates that one mechanism for protein stability control, at least for CBL calcium sensors, involves phosphorylation by their partner kinases . Although previous studies showed that the CBLs can be phosphorylated in vitro by their partner CIPKs, functional relevance of such phosphorylation is proposed to enhance interaction between CBLs and CIPKs in yeast and protoplast transient expression system or to play a role in activating AKT1 in Xenopus Oocytes. In this study, we identified specific CIPKs responsible for CBL phosphorylation in planta and provided a link between CBL phosphorylation and control of the protein stability in response to changing K+ status. Because the abundance of downstream kinases and transporters are also tightly associated with their phosphorylation status, we propose that the “CBL-CIPK-transporter” pathway represents a phosphorylation-dependent protein stabilization and activation cascade . Investigating the mechanism underlying regulated protein stability in response to K status and how different CIPK members may differentially regulate different CBLs will be a major direction to focus on in the future. For further understanding of phosphorylation-dependent protein stability control, we identified the kinases and phosphatases that contribute to the reversible phosphorylation of the CBL-type Ca2+sensors. It is particularly interesting to find that the CBLphosphorylating kinases are activated by the low-K+ stress and, in contrast, the PP2C phosphatases function in response to low- to high-K+ switch. Furthermore, it is significant to reveal that the CIPKs responsible for low-K+ response phosphorylated both the PM-CBLs and VM-CBLs ,macetero de 7 litros whereas the HAB1/ABI1/ABI2/PP2CA phosphatases involved in high-K+ response specifically act on the VM-CBLs . Such findings clearly indicate that highK+ -induced dephosphorylation are pathway-specific and does not simply represent a reverse mode of low-K+ -induced phosphorylation.

Taken together with previous finding that the high K+ -responsive PP2Cs have been shown to be critical regulators of ABA responses, we expect that K+ -nutrient sensing may crosstalk to ABA signaling through these and possibly other components. The finding that the addition of ABA to the high-K+ medium blocked the VM-CBL2/3 dephosphorylation and ABA deficient mutant aba2-1 showed a similar hypersensitive phenotype to cbl2/3 and cipk9/ 23 mutants supported this notion . Considering that these PP2C members can physically interact with both CIPKs and CBLs, and that HAB1/ABI1/ABI2/PP2CA repress the auto-phosphorylation of CIPK9 and CBL2/3 transphosphorylation , we proposed that HAB1/ABI1/ABI2/PP2CA phosphatases may control the phosphorylation levels of CBL2/3 by at least three possible mechanisms: by interacting and dephosphorylating CBL2/3 directly, by dephosphorylating and inhibiting CIPK9/23 kinase activity, and/or by sequestering CIPK9/23 proteins from binding to CBL2/3. Future work is thus expected to resolve these possibilities and to identify other early events in sensing K+ status in plants. Another significant finding in this work is the relationship between the dual CBL-CIPK pathways in response to low-K+ stress. Our recent study indicated that VM-CBL2/3-CIPK pathway is more critical than the PM-CBL1/9-CIPK pathway because cbl2cbl3 double mutant showed severe growth inhibition in a broad range of external K+ regimes whereas the cbl1cbl9 double mutant displayed much less defect under the same conditions. This is consistent with our results in this study that the activity of VM-CBL2/3-CIPK pathway is more sensitive to K+ deficiency and is activated earlier than PM-CBL1/9-CIPK pathway during high- to low-K+ transfer . These results further support the notion that VM-CBL2/3-CIPK pathway for K+ remobilization may serve as a primary mechanism for plants to respond andadapt to K+ -deficiency. Along this line, we also found that, although CBL2/3 and CBL1/9 are spatially separated in the cell, VM-CBL2/3 are essential for the stabilization of CBL1/9 proteins in response to low-K+ stress . Concerning the molecular link that enables such coordination between VM-CBL2/3-CIPK and PM-CBL1/9-CIPK pathways, we hypothesize that the partner kinases shared by CBL2/3 and CBL1/9, i.e., CIPK9/23, may serve as the “bridge” of the dual pathways. When plants face low-K+ stress, early signals, such as Ca2+ spikes, may first activate CBL2/3 that preferentially recruit CIPK9/23 kinases to the vacuolar membrane to phosphorylate and stabilize CBL2/3. Stable CBL-CIPK complexes phosphorylate and activate their target transporters such as TPKs to retrieve K+ from the vacuolar store. With prolonged K+ deficiency, the PM-CBL1/9 recruit the hyperactive CIPKs that may shuttle between VM and PM to form CBL-CIPK complexes at the plasma membrane where CIPKs phosphorylate CBL1/9 and K+ transporters, e.g., AKT1, boosting K+ uptake from K+ -limited environments.

Future work should be directed to monitoring the time course of low-K+ generated Ca2+ signature and its correlation with the sequential activation of VM-CBL-CIPK and PM-CBL-CIPK modules, as well as dissecting the possible “CIPK shuttling” mechanism between the VM and PM. Additionally, it would be interesting to explore the molecular toolkit for the production of Ca2+ signals that activate CBL2/ 3 and CBL1/9 in response to low-K+ stress.All seeds were surface sterilized with 10% bleach for 10 min, washed three times with water and sown on the growth medium solidified with 0.8% BD BBLTM select agar. The recipe of the growth medium was modified from MS medium with a reduced level of NH4 + unless indicated otherwise, which contained the following components: 3 mM Ca 2, 1.25 mM NH4H2PO4, 1.5 mM MgSO4, 1× Murashige and Skoog micronutrients , and 1% sucrose. The pH of the medium was adjusted to 5.8 using NaOH. The final K+ concentration in the medium was adjusted by adding KCl as the K+ source. For the germination phenotyping assay, seedings were germinated on modified MS medium shown above with different concentrations of K+ and incubated at 4 °C for 4 d for stratification, then were transferred to a growth chamber with 80 μmol m−2 s−1 light intensity with a 12 h light/ 12 h dark photoperiod for the indicated days. For the post-germination phenotyping assay, seeds were germinated on modified MS medium containing 20 mM K+ and grown for 4 days. The seedlings were then transferred onto various agarose-solidified modified MS medium 2, 1.25 mM NH4H2PO4, 1.5 mM MgSO4, 1× Murashige, and Skoog micro-nutrients, and 1% sucrose, pH5.8 supplemented with different concentrations of K+ for subsequent growth under 80 μmol m−2 s−1 light intensity with a 12 h light/12 h dark photoperiod. At the end of assay, the root length of seedlings was measured by Image J software. For phenotypic assay in the hydroponics, seeds were germinated on MS medium and grown for 7 days. The seedlings were then transferred to the liquid solution containing 1.4 mM Ca2, 0.1 mM Ca2, 0.125 mM MgSO4, 0.025 mM MgCl2, as well as 1/6 strength of MS minor salts and supplemented with different concentrations of KCl. All the hydroponic solutions for plant growth were replaced with fresh ones twice a week.Total RNA was extracted from plant samples using the TRIZOL reagent . After being treated with DNase I to remove DNA contamination, cDNA was synthesized using SuperScript II reverse transcriptase kit . The quantitative real-time PCR analysis was performed on the DNA Engine Opticon System using the SYBR Green Realtime PCR Master Mix .

All experiments were performed using three biological replicates,macetas 30 litros and actin served as an internal standard. The relative expression of each gene was calculated using ΔΔCT method. Each experiment was repeated with three different batches of samples and RT-PCR reactions were performed with three technical replicates for each sample. The primers used in quantitative real-time PCR are listed in Supplementary Table 1.For total protein extraction, Arabidopsis seedlings were grounded in the presence of liquid nitrogen to a fine powder and extracted with 2× SDS sample buffer . Aliquots of denatured total protein were separated by 12% SDS-PAGE and transferred to PVDF membrane. For the detection of phosphorylated CBL proteins, the total protein was separated by 10% SDS-PAGE with 15 μM Phos-tag and transferred to PVDF membrane. For immunoblot analyses, anti-CBL1, anti-CBL3, anti-β-tubulin , anti-GAPDH , anti-actin , anti-Flag were used as primary antibodies. The anti-CBL1 rabbit polyclonal antibody was made using recombinant CBL1 protein purified from E coli as antigen by Cocalico company . Each experiment was repeated at least three times, and one representative result was shown. Quantification of immunoblots was done using Image J software.Arabidopsis seedlings were grounded in the presence of liquid nitrogen to fine powder and extracted with buffer containing 50 mM HEPES , 150 mM NaCl, 50 mM β-glycerophosphate, 2 mM DTT, 1% Triton X-100 and 10% glycerol, with EDTA-free protease inhibitors . After centrifugation for 10 min at 20,000 g, the supernatant was isolated and used as protein samples for Phostag gel analysis. For dephosphorylation of CBL1/9 and CBL2/3, 50 μL supernatant was incubated with 1 μL λ-PPase and 5 μL 10 mM MnCl2 under 30 °C for the indicated times. For dephosphorylation of CIPK9-3Flag, CIPK23-3Flag, AKT1-3Flag proteins, the supernatant was incubated with 10 μL prewashed anti-Flag M2 agarose beads for 1 h at 4 °C on a roller shaker. The beads were then washed three times with the extraction buffer described above. The protein bound beads were incubated with 1 μL λ-PPase and 5 μL 10 mM MnCl2 under 30 °C for 30 min. The dephosphorylation reaction was stopped by adding 2× SDS loading buffer and boiled for 10 min.CIPK9, CBL2 and CBL3 were cloned in pGEX4T-1 vector and expressed in E.coli as a GST-tag fusion protein, ABI1, ABI2, PP2CA and HAB1 were cloned in pMAL-c2X vector as a MBP -tag fusion protein. All MBP- and GST-fused proteins were purified according to standard instructions. For in vitro phosphorylation, 0.5–2.0 mg of purified proteins was incubated in kinase reaction buffer containing 20 mM Tris , 2.5 mM MnCl2, 0.5 mM CaCl2, 1 mM DTT, 10 mM ATP and 2 μCi 32γP at 30 °C for 30 min and terminated by 5× SDS–PAGE loading buffer. The samples were subsequently analyzed using a 12% SDS-PAGE gel, followed by Coomassie staining and autoradiography. Coomassie staining was used to verify the quality of samples and loading consistency.To measure the K content, plant roots and shoots were harvested separately at the end of each phenotypic assay and surface-washed with double-distilled water for 30 s. The samples were then thoroughly dried in the oven at 99 °C. The dry tissues were grounded in a mortar, collected into a 15 ml tube, and dissolved with 1 ml ultrapure HNO3 . The tubes were incubated in a water bath at 99 °C for 4 h. Digested samples were diluted with double-distilled water and the K concentration in the solution were determined by inductively coupled plasma optical emission spectroscopy .In flowering plants, a primary role for boron is to form a diester cross-link between two monomers of rhamnogalacturonan-II , a pectic polysaccharide present in the cell walls of all vascular plants . Rhamnogalacturonan-II is a structurally complex domain of pectin , which comprises 12 different monosaccharides that are linked together by at least 20 different glycosidic linkages . Nevertheless, its structure is largely conserved in vascular plants . The majority of RG-II exists in the wall as a dimer that is generated by forming a borate diester between the D-apiose of side chain A of two RG-II molecules. The inability of RG-II to properly assemble into a dimer results in the formation of cell walls with abnormal biochemical and biomechanical properties and has a severe impact on plant productivity.Nevertheless, the mechanisms that drive the interactions between borate and RG-II are poorly understood . There is increasing evidence that alteration of RG-II structure and cross-linking have severe impacts on plant growth, development and viability. To date, the only characterized RG-II biosynthetic enzymes are the rhamnogalacturonan xylosyl transferases , which catalyze the transfer of xylose from UDP-xylose to fucose to form ɑ-xylose–fucose in vitro . Inactivation of RGXT1 and -2 has no discernible effect on plant growth or RG-II structure , implying redundancy of function, whereas mutations affecting RGXT4 lead to defects of root and pollen tube growth that are lethal . Mutations that prevent the synthesis of UDP-Api and CMP-Kdo are also lethal and provide further evidence for the essential role of RG-II in plant growth .

¿Qué opciones de proveedores existen para la compra al por mayor de macetas de plástico?

Existen diversas opciones de proveedores para la compra al por mayor de macetas de plástico. Aquí te presento algunas opciones comunes que puedes explorar:

  1. Fabricantes de macetas:
    • Muchos fabricantes especializados en productos para jardinería y horticultura ofrecen macetas de plástico al por mayor. Puedes buscar fabricantes en tu área local o contactar con aquellos que operen a nivel nacional o internacional.
  2. Distribuidores y mayoristas:
    • Algunos distribuidores y mayoristas se especializan en suministros para jardinería y pueden ofrecer una variedad de macetas de plástico al por mayor. Estos proveedores pueden ser una opción conveniente para obtener una amplia gama de productos.
  3. Plataformas en línea de comercio al por mayor:
    • Plataformas en línea como Alibaba, Global Sources y otras similares conectan a compradores y vendedores al por mayor. Puedes explorar catálogos, comparar precios y establecer contacto directo con fabricantes.
  4. Empresas de suministros para jardinería:
    • Empresas especializadas en suministros para jardinería y paisajismo a menudo ofrecen macetas de plástico al por mayor. Puedes buscar proveedores que se centren específicamente en la industria de la jardinería.
  5. Tiendas de suministros agrícolas y de jardinería:
    • Tiendas que se centran en la venta de suministros agrícolas y de jardinería pueden tener secciones dedicadas a macetas de plástico al por mayor. Algunas de estas tiendas también pueden ofrecer descuentos por volumen.
  6. Ferias y eventos de la industria:
    • Asistir a ferias y eventos de la industria de jardinería,macetas 25 litros agricultura o horticultura te brinda la oportunidad de conocer directamente a fabricantes y proveedores, ver sus productos y establecer relaciones comerciales.
  7. Redes de contactos y referencias:
    • Pregunta a colegas de la industria, paisajistas, viveros y otros profesionales del sector si tienen recomendaciones de proveedores confiables. Las referencias personales pueden ser valiosas para encontrar opciones de calidad.
  8. Cooperativas agrícolas:
    • Algunas cooperativas agrícolas y grupos de productores pueden tener acceso a proveedores de macetas de plástico al por mayor. Investigar en el ámbito local puede ser beneficioso.

Antes de tomar una decisión, asegúrate de investigar a fondo a los proveedores, verificar la calidad de sus productos, revisar términos y condiciones, y comparar precios. También puedes solicitar muestras para evaluar la calidad antes de realizar pedidos a gran escala. La transparencia y la comunicación abierta son fundamentales en cualquier relación comercial al por mayor.

¿Hay opciones personalizadas para macetas plásticas por mayor?

Sí, muchos proveedores y fabricantes ofrecen opciones personalizadas para macetas plásticas al por mayor. Estas opciones permiten adaptar las macetas a las necesidades específicas de los clientes, ya sea con respecto al tamaño, diseño, color, logotipo u otros detalles. Aquí hay algunas formas en que puedes personalizar macetas plásticas al por mayor:

  1. Impresión de Logotipo o Etiqueta: Puedes solicitar la impresión del logotipo de tu empresa o una etiqueta personalizada en las macetas. Esto es ideal para eventos promocionales, regalos corporativos o para impulsar la marca.
  2. Colores Personalizados: Algunos proveedores permiten la personalización del color de las macetas. Puedes elegir colores que se alineen con la identidad de tu marca o que se adapten al tema de tu proyecto.
  3. Tamaños y Formas Específicas: Si necesitas tamaños o formas específicas que no están disponibles en el inventario estándar, muchos proveedores pueden personalizar las macetas según tus especificaciones.
  4. Materiales Específicos: Puedes solicitar macetas plásticas fabricadas con materiales específicos que se adapten a tus necesidades, como plásticos reciclados, biodegradables u otros materiales ecológicos.
  5. Diseños Especiales: Si tienes un diseño específico en mente, algunos fabricantes pueden trabajar contigo para crear macetas con diseños únicos,macetas 7 litros patrones o características especiales.
  6. Agregado de Funcionalidades Especiales: Algunos proveedores ofrecen opciones personalizadas, como macetas con sistemas de riego automático, compartimentos adicionales, o características específicas para facilitar el cuidado de las plantas.
  7. Embalaje Personalizado: Además de personalizar las macetas en sí, puedes solicitar un embalaje personalizado que refleje tu marca o incluya información específica.

Antes de solicitar opciones personalizadas, es importante comunicarte directamente con los proveedores, discutir tus requisitos y confirmar los detalles del proceso de personalización. Además, ten en cuenta que las opciones y los costos pueden variar según el proveedor y la cantidad solicitada.

Cultivo de bayas en macetas: Consejos para cultivar arándanos y frambuesas con éxito

La jardinería en recipientes abre interesantes posibilidades para cultivar deliciosas bayas, ofreciendo una solución para aquellos con espacio limitado o condiciones de suelo menos que ideales. Los arándanos y las frambuesas, conocidos por su sabor dulce y ácido, pueden cultivarse con éxito en recipientes con los cuidados y la atención adecuados. En este artículo, exploraremos el potencial del cultivo de arándanos y frambuesas en macetas,maceta 25l junto con consejos esenciales para una cosecha próspera.

Arándanos en contenedores:

Selección de contenedores:

Elija recipientes grandes con un tamaño mínimo de 5 galones para cada planta de arándanos. Opta por recipientes de materiales duraderos, como plástico o cerámica, y asegúrate de que tengan agujeros de drenaje para evitar que se encharquen.
Mezcla de tierra:

Utilice una mezcla de tierra ácida y con buen drenaje diseñada específicamente para los arándanos. Puedes encontrar fórmulas premezcladas o crear la tuya propia combinando musgo de turba, corteza de pino y perlita. Mantener el pH adecuado (entre 4,0 y 5,5) es crucial para el éxito de los arándanos.
Requisitos de luz solar:

Los arándanos crecen bien a pleno sol. Coloque las macetas en un lugar donde reciban al menos 6-8 horas diarias de luz solar directa. Considere la posibilidad de rotar los recipientes de vez en cuando para garantizar una exposición uniforme.
Riego:

Los arándanos prefieren un suelo constantemente húmedo pero no encharcado. Riegue en profundidad cuando la capa superior del suelo esté seca. Cubra la superficie con paja de pino o virutas de madera para retener la humedad y eliminar las malas hierbas.
Abonado:

Utilice un fertilizante de liberación lenta y formación ácida formulado específicamente para los arándanos. Aplíquelo siguiendo las instrucciones del envase, normalmente en primavera y a principios de verano. Evite fertilizar en exceso, ya que esto puede provocar desequilibrios de nutrientes.
Poda:

Pode las plantas de arándanos para mantener una forma compacta y fomentar el desarrollo de nuevos brotes. Elimine las ramas muertas o débiles y aclare las zonas abarrotadas para mejorar la circulación del aire.
Frambuesas en contenedor

Tamaño del contenedor:

Las frambuesas se adaptan mejor a la jardinería en recipientes que los arándanos. Seleccione recipientes con un tamaño mínimo de 15-20 galones para cada planta de frambueso. Los recipientes más grandes ofrecen más espacio para el sistema radicular de la planta.
Mezcla de tierra:

Utilice una mezcla para macetas con buen drenaje y rica en materia orgánica. Una mezcla de compost, tierra de jardín y perlita o vermiculita funciona bien. Asegúrese de que el pH de la tierra esté entre 5,5 y 6,5 para un crecimiento óptimo de la frambuesa.
Luz solar y temperatura:

Los frambuesos crecen bien a pleno sol, pero pueden tolerar la sombra parcial. Asegúrese de que sus macetas reciban al menos 6 horas diarias de luz solar. Considere la posibilidad de colocar las macetas estratégicamente para proteger las plantas del intenso calor de la tarde en climas más cálidos.
Riego:

Las frambuesas prefieren una humedad constante, especialmente durante la época de fructificación. Riegue cuando la capa superior del suelo esté seca y cubra la superficie con mantillo para retener la humedad. Tenga cuidado de no regar en exceso,cultivo de frambuesas ya que las frambuesas son susceptibles a la pudrición de la raíz en condiciones de encharcamiento.
Estructuras de soporte:

Instala un enrejado o un sistema de soporte para las frambuesas con el fin de evitar que las plantas se vuelvan pesadas a medida que crecen. Esto es crucial para soportar el peso de los tallos cargados de fruta.
Poda:

La poda regular es esencial para los frambuesos. Elimine los tallos gastados después de la fructificación y corte las ramas laterales para estimular el crecimiento. Esto ayuda a mantener la salud de la planta y promueve una mejor producción de fruta.
Consejos generales para el cultivo de frambuesas en contenedores:

Polinización:

Las bayas cultivadas en contenedor pueden beneficiarse de la polinización manual, especialmente si cultiva variedades que no se autopolinizan. Agite suavemente las plantas o utilice un cepillo suave para transferir el polen entre las flores.
Protección invernal:

En los climas más fríos, aísle los recipientes para proteger las raíces de las temperaturas bajo cero. Traslade las macetas a un lugar protegido o envuélvalas con arpillera para aislarlas.
Controle los niveles de pH:

Compruebe con regularidad los niveles de pH de la tierra de sus contenedores para asegurarse de que se mantienen dentro de los límites recomendados para cada tipo de baya. Ajústelo si es necesario utilizando enmiendas como azufre o cal.
Rote los recipientes:

Gire los recipientes de vez en cuando para favorecer una exposición uniforme a la luz solar en todos los lados de las plantas. Esto ayuda a evitar un crecimiento desigual y garantiza que todas las partes de la planta reciban la luz solar adecuada.
Inspecciones periódicas:

Vigile de cerca sus bayas cultivadas en contenedor para detectar signos de plagas o enfermedades. La detección precoz permite intervenir con rapidez y mantener la salud de las plantas.
Conclusión:

Cultivar arándanos y frambuesas en recipientes no sólo es factible, sino también gratificante. Con la elección adecuada de recipientes, mezclas de tierra y un cuidado diligente, podrá disfrutar de una abundante cosecha de bayas frescas cultivadas en casa. Tanto si dispone de un pequeño patio como de un balcón, la jardinería en recipientes es una solución versátil para llevar el delicioso sabor de los arándanos y las frambuesas hasta la puerta de su casa.

Mastering Hydroponics: A Guide to Successful Indoor Growing

The homogenate was centrifuged at 13,000 g and 4 °C for 20 min. The activity of glycosyltransferase was measured immediately by mixing 100 µL of supernatant with 0.95 mL of the reaction mixture containing 50 mM PBS , 2 mM MgCl2, 2 mM uridine 5′-diphosphoglucose, 3.125 mM 4- nitrophenyl β-D-glucuronide, 3.125 salicin and 0.95 mL of 1 mM 2,4,5-trichlorophenol . The assay mixture was incubated at 30 °C for 30 min, and then stopped by adding 10 µL of phosphoric acid. After centrifugation at 13,000 g for 5 min, the supernatant was collected and diluted with HPLC grade acetonitrile and 0.1% trifluoroacetic acid . The enzyme activity was determined using an Agilent 1200 series HPLC paired with UV detector and a Thermo Scientific Acclaim™ 120 C18 5-µm column . An isocratic flow was set with 1 mL min-1 70:30 mobile phase A and mobile phase B for 10 min. The TCP-glucoside was detected at 205 nm. A six-point TCP standard calibration curve was used to determine activity. All treatments in the A. thaliana cell incubation experiment were conducted in triplicate, and all hydroponic cultivations were conducted using four replicate jars containing individual plants to account for potential loss of plants. Calibration curves with standards of diazepam, diazepam-d5, nordiazepam, temazepam, oxazepam and oxazepam-glucuronide were used for quantification with the r 2 values of at least 0.99 for all analytes. A limit of detection of 1 ng mL-1 and a limit of quantification of 3 ng mL-1 for diazepam and its metabolites were determined through preliminary experiments. For oxazepam-glucurnonide the LOD was 3 ng mL-1 and the LOQ was 5 ng mL-1 . LODs and LOQs were calculated based on a signal to noise ratio of 3 and 10, respectively. Individual peaks were detected and integrated using TargetLynx XS software from MassLynx platform . Data were analyzed with StatPlus and graphed using Prism 6 GraphPad software . Results were calculated as the mean ± standard deviation . The Student’s t-test was used to test significant differences in the extractable and non-extractable radioactivity and glycosyltransferase activity at α = 0.05. Systematic differences in the concentration of diazepam in plant tissues were assessed using one-way ANOVA with Fisher’s Least Significant Difference post-hoc .Active plant metabolism of diazepam was validated using a range of controls.

No diazepam was detected in the non-treated media or the cell blanks,hydroponic grow kit and there was no significant degradation of diazepam in the cell-free media, suggesting no contamination or significant abiotic transformation. Moreover, no significant difference was seen in cell mass between the chemical-free control and the treatments, indicating that diazepam did not inhibit the growth of A. thaliana. Furthermore, no significant amount of diazepam was adsorbed to the cell matter in the non-viable cell control. In contrast, diazepam dissipated appreciably from the media containing viable cells, with the average concentration decreasing from 698 ± 41.5 to 563 ± 8.93 ng mL-1 after 120 h of incubation, a decrease of nearly 20% . Parallel with the dissipation in the medium, diazepam was detected in the A. thaliana cells, with the highest level appearing after 48 h and a substantial decrease thereafter . The decrease in diazepam level in the cell fit a first-order decay model and yielded a half-life of about 68 h . This half-life was in comparison to a biological half-life of 48 h in humans , indicating a moderate persistence in plant cells. Out of the four known diazepam metabolites only nordiazepam and temazepam were detected in the A. thaliana cells over the 120 h incubation. Temazepam was detected first, with the highest concentration being observed at 12 h, which was followed by a decrease to 58.6 ± 17.0 ng g-1 at the end of the 120 h cultivation. Nordiazepam gradually increased over the 120 h incubation time from 128 ± 61.0 ng g-1 at 6 h to 535 ± 92.0 ng g-1 at the end of incubation . These results correlated with their behavior in the human body, as nordiazepam displayed one of the most prolonged biological half-lives of the benzodiazepine family , while temazepam had a significantly shorter half-life . The parallels observed between human and plant metabolism in this study and others is intriguing, as it indicates that we may be able to use the knowledge of biologically active metabolites formed during human metabolism as a guide to study their formation and longevity in environmental compartments such as higher plants. The complementary use of 14C labeled diazepam facilitated the determination of the fraction of diazepam and its metabolites that were incorporated into the cell matter , which could not be determined using traditional extraction and analytical methods. We observed that the radioactivity in the media decreased while the extractable and bound residue fractions increased over the 120 h incubation .

The extractable radioactivity in the viable cells increased to 113 ± 31 dpm g-1 at 120 h . The bound residues increased steadily to a final level of 1120 ± 224 dpm g-1 , indicating that A. thaliana cells were capable of metabolizing and then sequestering diazepam and its metabolites, likely invacuoles and cell walls. The formation of these bound residues is commonly regarded as a detoxification pathway of xenobiotics in higher plants. Diazepam was found in the cucumber and radish seedlings following a 7 d cultivation at the higher concentration and a 28 d of cultivation following treatment at the lower concentration . After treatment with 1 mg L-1 with diazepam for 7 d, a significantly higher concentration of diazepam was observed in the roots as compared to the shoots in radish seedlings whereas diazepam was more evenly distributed throughout the entire plant of cucumber seedlings . However, after the 28 d cultivation following the lower concentration treatment, this pattern appeared to be different for both plant species. In the radish plants, diazepam was more evenly distributed in the roots, but was significantly lower in the shoots . In the cucumber plants there was a significantly higher concentration in roots and a significantly lower concentration in the shoots . These differences may be due to variations in metabolism between the two species, as well as dynamic changes as a function of contact time in both plant growth and its ability to metabolize and translocate diazepam. Similar metabolites to those in A. thaliana cells were found in seedlings grown in the nutrient solution spiked with diazepam, with nordiazepam being predominant . In the 7 d and 28 d cultivation experiments, temazepam was found to be the second major metabolite in the leaves of the cucumber seedlings, and the level was higher in the 7 d cucumber seedlings than the 28 d plants . Oxazepam was detected in the leaves of both plant species after the 7 d cultivation . The higher accumulation of diazepam and the biologically active metabolites in the leaves may have ecotoxicological ramifications; for example, many insects consume leaves, even if they are not edible tissues for humans . Our results were in agreement with recent findings in Carter et al. , in which they observed the formation of nordiazepam,hydroponic indoor growing system temazepam and oxazepam in radish and silver beet plants exposed to diazepam and chlordiazepoxide. They similarly showed nordiazepam to be the major metabolite with oxazepam and temazepam constituting a much smaller fraction at the end of 28 d cultivation in soil. However, in that study, the authors did not track the formation of these metabolites over time or influence of treatment concentrations.

Phase III metabolism appeared to increase from the 7 d to 28 d cultivation for both radish and cucumber seedlings . Between the plant species, the cucumber seedlings had a greater fraction of non-extractable radioactivity in comparison to the radish seedlings . In the 7 d cultivation experiment, the mass balances came to 99.3% for the cucumber plants but only 58.1% for the radish seedlings . Due to the multiple water changes , a complete mass balance was not attainable for the 28 d cultivation experiment. However, when a proxy mass balance was calculated for both species, a similar pattern was observed. A total of 83.0% of the added 14C radioactivity was calculated for the cucumber treatments while the fraction was 61.3% for the radish plants. This could be due to increased mineralization in the growth media and respiration of 14CO2 through plant in the radish cultures. As mineralization is viewed as the final stage of detoxification , it is likely that the radish plant was more efficient in their ability to detoxify diazepam than cucumber plants. The Brassicaceae family, which includes the common radish, has been shown to be effective for phytoremediation due to their possession of genes that increase tolerance to stressors and activation of enzymes capable of extensive bio-transformations .No detectable level of oxazepam-glucuronide was observed in radish or cucumber seedlings for either the 7 d or 28 d cultivation. However, there was a significant difference in the glycosyltransferase activity in radish seedlings treated with diazepam for 7 d and 28 d, although a distinct pattern in the changes of the enzyme activity was absent . For the 7 d cultivation experiment, a significant decrease in glycosyltransferase activity was observed in the shoots of radish seedlings when compared to the control . In contrast, no significant change in glycosyltransferase activity was observed in the shoots of cucumber seedlings when exposed to diazepam . In the 28 d cultivation experiment, only the cucumber seedlings exhibited significant differences in the enzyme activity, with an increase in activity detected in the shoots and a decrease in the cucumber buds . Even though we did not detect oxazepam-glucuronide in the exposed plants, changes in the glycosyltransferase activity indicated that conjugation might have occurred with the parent and its metabolites, including those not examined in this study, or at levels below our detection capability. In addition, it may be postulated that rapid phase III metabolism may have limited the accumulation of such conjugates in the plant tissues, making the conjugates transient metabolites. In previous studies, glycosyltransferase was observed to catalyze the detoxification of ibuprofen in Phragmite australis during a 21 d exposure . Further, the formation of a glucose conjugate has been considered to be a major detoxification pathway for several environmental contaminants . These studies together suggest the importance of phase II metabolism in the metabolic fate of pharmaceuticals in higher plants. Water scarcity has led to continuously increasing use of municipally treated wastewater in agro-environments, especially in arid and semi-arid regions . Similarly, the use of municipal bio solids to improve soil health is increasing . The land application of TWW and bio solids can introduce contaminants of emerging concern into terrestrial environments . Consequently, a range of CECs have been detected in agricultural soils . Literature pertaining to the effects of CECs in terrestrial ecosystems is, however, limited . The majority of previous research has been concerned with the fate and effects of CECs in plants , and only a few studies have considered CECs in terrestrial invertebrates . One of the most important invertebrates in agricultural fields is earthworm. Earthworms ameliorate agricultural soil structure through the formation of new aggregates and macropores; improving soil tilth, aeration, infiltration, and drainage . Furthermore, earthworms consume plant litter, recycle organic matter and aid in nutrient cycling . Earthworms dominate soil fauna with an average biomass of 10 – 200 g m-2 . Due to their ecological importance and abundance, earthworms are a good candidate for ecotoxicity testing . Herein we sought to understand some of the potential consequences of CECs exposure in earthworms. For this study, we selected theearthworm species Eisenia fetida as the test organism due to their widespread use in the scientific literature and extensive habitat range. For CECs, we considered three pharmaceuticals, i.e., naproxen, diazepam, and sulfamethoxazole, and one cosmetic preservative, i.e., methyl paraben. These four compounds were selected due to their range of physicochemical properties and frequent detections in the environment . Naproxen is a commonly consumed nonsteroidal anti-inflammatory drug that has been often found in TWW and bio solids . Diazepam is a psychoactive compound from one of the most commonly prescribed classes of pharmaceuticals of wastewater treatment plants. Diazepam has also been frequently detected in TWW due to poor removal efficiency . Sulfamethoxazole is an antibiotic and has garnered significant scientific interest due to the growing concern over antibiotic resistance .

From Roots to Results: Understanding the Principles of Hydroponic Cultivation

Mn3O4 NPs also possess excellent ROS-scavenging capacities, exerting multiple enzyme mimicking activities, for example, SOD- and CAT-like, as well as hydroxyl radical scavenging activities. A recent study reported that foliar application of Mn3O4 NPs at 1 mg per plant significantly alleviated salinity stress of cucumber plants. The authors found that Mn3O4 NPs increased endogenous low-molecular-weight antioxidants in the leaves, including resveratrol, chlorogenic acid, dihydroxycinnamic acid, benzenetriol, hydroxybenzoic acid, trihydroxybenzene, quinic acid and catechin. The multifunctional catalytic behaviour of Mn3O4 NPs arise from the coexistence of Mn and Mn oxidation states, and the switch between the II and III valence resembles the mechanism of redox enzymes, which is very similar to CeO2 NPs. In addition to directly acting as ROS-scavenger, NMs can act as carriers to deliver ROS-eliminating compounds to enhance plant stress tolerance. The authors of a recent study designed an ROS-responsive star polymer that successfully alleviated plant stress by simultaneous ROS-quenching and nutrient release. Specifically, RSP was foliar-applied to stressed tomato leaves. The RSP penetrated the leaf epidermis and entered into the chloroplasts where it efficiently eliminated H2O2, which subsequently triggered the release of the nutrient from the polymer. This study highlights the potential of using RSP as an ROS-responsive NM to manage short-term plant stress. Apart from foliar application, ROS-scavenging CeO2 NPs have been applied to roots. It has been reported that CeO2 NPs at 100 and 500 mg l−1 applied to hydroponic cultivated rice can significantly increase the nitrogen levels in roots and shoots by 6–12% and 22–30%, respectively, compared with controls. Similarly, ref. added graphene to the growth media of alfalfa ,macetas redondas and found that the amendment alleviated salinity and alkalinity stresses by modulating antioxidant defence systems and genes related to antioxidant defence and photosynthesis.

The treatment of graphene significantly increased dry biomass of alfalfa by 29.4% and 24.3%, respectively, in salinity and alkalinity conditions. In another study, root delivery of ROS-eliminating CeO2 NPs to hydroponically cultivated rice plants was shown to improve rice tolerance under salinity stress, increasing chlorophyll content and yield. ROS-scavenging NMs have also been reported as a seed treatment agent to improve stress resistance. For example, ref. found that cotton seeds primed with poly-coated CeO2 NPs at 500 mg l−1 for 24 h exhibited significantly increased root vitality by 114% under salt stress. Similarly, ref. found that salt-sensitive rapeseeds seeds primed with poly-coated CeO2 NPs exhibited enhanced salt tolerance by modulating ROS homeostasis. These studies suggest that using ROS-scavenging NMs to treat seeds can alleviate stress at germination stage , although the duration of this protective benefit is currently unknown. Figure 3 summarizes the current known or hypothesized mechanisms by which ROS-scavenging NMs alleviate plant stress.ROS are important signalling molecules that mediate redox signalling pathways and contribute to acclimatization against a range of stresses. One study demonstrated that an ROS wave is required to activate systemic acquired acclimation of plants to heat or high light stresses, highlighting the important biological function of this signalling molecule to the acclimation against abiotic stresses. In addition, an ROS-generating-associated gene respiratory burst oxidase homologue has been shown to be critical to plant stress responses. Given the known response of plants to select lower-level ROS that elicit redox signalling pathways, the concept of pretreating or priming plants with ROS-triggering NMs to stimulate defence systems and acquire systemic acquired acclimation may be an effective strategy to increase stress tolerance. In this strategy, plant stress resistance will be acquired via the initiated adaptive responses by ROS-triggering NMs. ROS-triggering NMs could be used to prime plants through a ‘stress memory’, which provides a mechanism for acclimation and adaptation, thereby improving the tolerance/avoidance abilities. Whereas ROS-scavenging NMs serve as a ‘curative’ strategy, ROS-triggering NMs are more like a ‘preventive’ strategy. Currently, only a limited number of studies have employed ROS-triggering nanozymes to increase plant stress resilience, and the researchers are primarily focusing on silver nanoparticles . AgNPs are known to catalyse ROS generation in cells.

A previous study reported that seed priming with AgNPs enhanced the tolerance of pearl millet to salinity stress by activating the antioxidant enzymes. AgNP seed priming significantly increased the fresh and dry weights of plants by 58% and 34%, respectively, compared with plants grown in 150 mM salt. The underlying mechanisms may be that AgNPs activated defence pathways during seed priming, forming the ‘stress memory’ and subsequently enhancing resilience to stress. The mechanisms for AgNPs generating ROS have been reported in recent studies. By using electron spin resonance, ref. demonstrated that AgNPs can directly produce • OH in the presence of H2O2, and Ag is generated during this process; importantly, Ag ions did not catalyse the production of • OH. Similar results were obtained by another study. A more recent study demonstrated that AgNPs possess peroxidase-mimicking activities, which catalyse oxidation of substrate TMB in the presence of H2O2. The formation of • OH by AgNPs is similar to a Fenton reaction in which AgNPs act as a Fenton-like reagent. Under a changing climate, the frequency of seed exposure to abiotic stresses will increase, which could result in reduced germination and loss of vigour, threatening crop yield. As such, accelerating the germination speed and enhancing the seed vigour are critical. One study reported that AgNP seed priming accelerated the germination speed and yield of Chinese cabbage . Another study showed that AgNP priming promoted the germination, growth and yield of watermelons . Nanoscale zero valent iron , also known to be a Fenton-like reagent, can catalyse the generation of ROS. Another study used nZVI as an ROS-modulator to pretreat rice seeds. This study found that priming generated an optimum level of endogenous ROS via Fenton’s reaction, resulting in higher seed germination rate and greater seed vigour. Unfortunately, the study did not further evaluate whether nZVI priming can increase the stress tolerance of seeds or seedlings, but given the observed hormone biosynthesis upregulation and increased antioxidant enzyme activity, nZVI seed priming should be explored as a potential strategy to promote the stress tolerance of rice and other plant species. Collectively, ROS-modulating NM-based seed treatments may be a promising strategy to mitigate climate-change-associated stress. Under stress conditions, although ROS over-accumulation is common, ROS can still act as signalling molecules, which interplay with other signalling molecules such salicylic acid to activate defence-related genes.

These metabolic processes help plants to establish systemic acquired acclimation or systemic acquired resistance, enhancing the resistance to abiotic or biotic stresses. Therefore, NMs that can trigger the upregulation of defence-related hormones/ signalling molecules or genes may also enhance stress resistance. One study reported that silica nanoparticles at 100 and 1,000 mg l−1 enhanced disease resistance of Arabidopsis plants by up-regulating the production of salicylic acid, a defence hormone and an important signalling molecule. Similarly, another study demonstrated that copper-based NMs successfully alleviated damage of soybeans to sudden death syndrome by triggering the upregulation of a broad array of defence-related genes . One study reported that foliar spray of commercial Cu2 nanoparticles significantly increased antioxidant defence-related genes, for example, SOD, GPX, MDAR and WRKY transcription factor, in cucumber plants, although the potential benefits to stress tolerance were not evaluated. Taken together, these studies demonstrate that NMs that can trigger ROS production or stimulate defence pathways can activate systemic acquired resistance of plants, enhancing the protection against disease or stresses through a classic adaptation response .For both ROS-scavenging NMs and ROS-triggering NMs, efficiently penetrating barriers and entering into plant cells is critical for modulating ROS levels and participating in metabolic activities. As such, an in-depth understanding of the uptake pathways of NMs is fundamental for the efficient application of nanobiotechnology in agriculture. Here, we briefly discuss the possible uptake pathways for NMs into plants, including foliar,maceta de 10 litros root and seed application . Foliar application has been the most extensively used delivery pathway. There are several pathways for the entry of nanoscale particles into leaves, including the cuticle and stomata. One study reported that foliar-applied gold nanoparticles in wheat can reach the mesophyll by either the cuticle or stomata, and move through the plant vasculature. Recent studies have noted that the stomatal uptake pathway is more efficient than the cuticle for Cu-based NPs. In addition, nanoparticle properties and leaf biointerface are important factors influencing the uptake and translocation of NPs. More mechanisms for foliar-uptake pathways can be referenced to excellent reviews. Compared with foliar application, delivering ROS-modulating NMs to plants via the roots has been less investigated. It has been reported that the application of ROS-modulating NMs to plant roots is more effective under hydroponic cultivation than under soil-grown conditions. In the soil system, NMs will undergo aggregation, adsorption and dissolution, confounding interaction with plant roots. A recent study compared the leaf and root application of ROS-scavenging CeO2 NPs on alleviating salt stress of cucumber, and found that foliar-sprayed CeO2 NPs enabled better cucumber salt tolerance than root application. The pathways for NMs entering into the root include apoplastic and symplastic pathways. Using ROS-modulating NMs to prime seeds could be a more cost-effective and environmentally friendly strategy than foliar and root application. This type of approach would not only reduce the release of engineered NMs in the environment but would also result in decreased worker exposure to these materials. Using ROS-modulating NMs to treat seeds might be a promising strategy to increase seed quality, promote growth and increase the yield. Additionally, nano-enabled seed treatment is an efficient way to load mineral nutrients into seeds.

By using transmission electron microscopy, one study observed that FeNPs were absorbed on the watermelon seed coat during the priming process and slowly translocated into the seed endosperm. By using transmission electron microscopy with energy-dispersive X-ray spectroscopy, another study also demonstrated the presence of FeNPs inside the seeds after the priming. These results demonstrate that NPs can effectively penetrate the seed coat and enter into seeds, although the mechanisms of action remain unclear and must be evaluated.Using NMs to modulate ROS homeostasis is a promising strategy to enhance stress tolerance of crop species. It is a rapidly developing area of research, with the vast majority of publications dating from only 2017 to 2022. We propose that additional mechanistic studies are needed to explore the potential of this approach. First, compared with the ROS-scavenging NMs strategy, the ROS-triggering NMs approach remains largely unexplored. Using ROS-triggering NMs to stimulate defence pathways at early growth stage, for example, seed or seedling, could enhance the immunity or resistance of plants to abiotic and biotic stresses. This ‘preventive’ strategy combined with an ROS-scavenging NM-based ‘recovery’ strategy may provide a versatile and effective solution for stress tolerance. Notably, ROS-scavenging nanozymes can sometimes also induce early ROS stimulation to enhance plant stress tolerance. As such, ROS-scavenging nanozymes could be applied as a ‘preventive’ strategy as well. In addition, ROS-triggering NMs may temporarily shift energy and resources to defence pathways, potentially impacting carbon and nitrogen metabolism in ways that could compromise biomass accumulation. As such, the regimen of application will be highly important. For example, one could apply ROS-triggering NMs simultaneously with nutrients in order to more broadly support the plant’s defence system. Abiotic stresses often occur in combination or in succession, and as such, future studies need to evaluate the performance of ROS-modulating NMs under multiple stressor scenarios. Furthermore, a comprehensive understanding of the mechanisms for modulating ROS via NMs to enhance plant stress tolerance is needed prior to deployment of these strategies in the field. The relevant mechanisms include the following: the pathway for NM entry into leaves,roots and especially seeds; the catalytic mechanisms of nanozymes, and how the size, surface charge, pH and environmental conditions impact the catalytic activities of NMs; the intracellular kinetics of ROS-scavenging or ROS-triggering mechanisms of NMs; the precise metabolic pathways by which ROS-triggering NMs enhance plant stress resistance ; and the cellular, biochemical and molecular level response of plants to NMs under different treatment regimens, especially transcriptome and metabolic reprogramming induced by ROS-triggering NMs. The orthogonal approach of transcriptomics, proteomics, metabolomics and epigenetics will be a powerful tool to address these questions. Nano-enabled stress tolerance strategies represent a rapidly developing interdisciplinary field of research. We need to pay attention to new findings from both plant and NMs fields, for instance, new knowledge regarding the response mechanism of plants to abiotic and biotic stresses, and state-of-the-art ROS-regulating nanozymes, which will push forward the application of nanozymes in crop stress tolerance. For example, a study recently reported that Huanglongbing, a devastating disease of citrus, is an immune-mediated disease that stimulates the production of ROS as well as the upregulation of genes encoding ROS-producing NADPH oxidases.

Innovative Growth: Hydroponic Agriculture and the Future of Farming

The Cu grains have about the same size as the electron-dense Cu granules in cells of E. splendens placed in a CuSO4 solution for 30 days .While biological activity clearly modified the original distribution of Cu in the rhizospheres, the Cu species could not be identified from the µ-XRF maps but instead were elucidated using EXAFS spectroscopy. All eight µ-EXAFS spectra from areas in the original soil containing the particle morphologies and chemical compositions observed with µ-XRF can be superimposed on the soil’s bulk EXAFS spectrum , indicating that the initial Cu speciation occurred uniformly. If the initial soil contained various assemblages of Cu species that were distributed unevenly, then we might expect that the proportions of species also would have varied among analyzed areas and been detectable by µ-EXAFS spectroscopy ; however, this was not observed. These spectra match those for Cu2+ binding to carboxyl ligands in natural organic matter, as commonly observed . Elemental Cu. In contrast, only the reference spectrum of elemental copper matches the µ-EXAFS spectra of the 12 hot-spot Cu grains, which are statistically invariant . Photo reduction of Cu2+ in the X-ray beam cannot explain the formation of Cu0 because no elemental Cu was detected in the initial soil by powder and µ-EXAFS, and Cu0 was detected in the two phytoremediated soils at 10 K by bulk EXAFS, and all individual spectral scans from the same sample could be superimposed. At 10 K, radiation damage is delayed , and if Cu had been reduced in the beam, the proportion of Cu0 would have increased from scan to scan which was not observed.The rhizospheres were oxidizing as indicated by the presence of iron oxyhydroxide , absence of sulfide minerals, and the fact that P. australis and I. pseudoacorus are typical wetlands plants with aerenchyma that facilitate oxygen flow from leaves to roots . Thermodynamic calculations using compositions of soil solutions collected below the rhizosphere indicate that Cu+ and Cu2+ species should have been dominant . These points along with the occurrences of nanocrystalline Cu0 in plant cortical cells and as stringer morphologies outside the roots together suggest that copper was reduced biotically. Ecosystem ecology of the rhizosphere indicates synergistic or multiple reactions by three types of organisms: plants, endomycorrhizal fungi, and bacteria.

Normally, organisms maintain copper homeostasis through cation binding to bio-active molecules such as proteins and peptides. When bound,plastic pots for planting the Cu2+/Cu1+ redox couple has elevated half-cell potentials that facilitate reactions in the electron-transport chain. Even though average healthy cell environments are sufficiently reducing , there are enough binding sites to maintain copper in its two oxidized states. Copper is also important in controlling cell-damaging free radicals produced at the end of the electron-transport chain, for example in the superoxide dismutase enzyme Cu-Zn-SOD, which accelerates the disproportionation of superoxide to O2 and hydrogen peroxide. However, unbound copper ions can catalyze the decomposition of hydrogen peroxide to water and more free radical species. To combat toxic copper and free radicals, many organisms overproduce enzymes such as catalase, chelates such as glutathione, and antioxidants . Mineralizationcould also be a defense against toxic copper, but reports of Cu+ and Cu2+ biominerals are rare; only copper sulfide in yeast and copper oxalate in lichens and fungi are known. Atacamite 3Cl in worms does not appear to result from a biochemical defense. Biomineralization of copper metal may have occurred by a mechanism analogous to processes for metallic nanoparticle synthesis that exploit ligand properties of organic molecules. In these processes, organic molecules are used as templates to control the shape and size of metallic nanoparticles formed by adding strong reductants to bound cations. For copper nanoparticles and nanowires, a milder reductants ascorbic acids has been used. Ascorbic acid, a well-known antioxidant, reduces Cu cations to Cu0 only when the cations are bound to organic substrates such as DNA in the presence of oxygen in the dark or via autocatalysis on Cu metal seeds in the absence of stabilizing organic ligands . As an example of synthetic control, pH dependent conformation of histidine-rich peptides has led to larger nanocrystals of Cu0 at pH 7–10 than at pH 4–6 . Plants produce ascorbic acid for many functions and rhizospheres often contain the breakdown products of ascorbic acid, which facilitates electron transfer during mineral weathering . Plants produce more ascorbic acid when grown in soils contaminated with heavy metals including copper . Fungi, which proliferate over plants and bacteria in metal-contaminated soils, can stabilize excess copper by extracellular cation binding or oxalate precipitation , but mechanisms probably also require enzymes, thiol-rich proteins and peptides, and antioxidants .

The formation of electron-dense Cu granules within hyphae of arbuscular mycorrhizal fungi isolated from Cu- and As-contaminated soil suggests that fungi also can produce nanoparticulate copper. Some copper reduction possibly occurred in response to the European heat wave of the summer of 2003 . Elevated expression of heat shock protein HSP90 and metallothionein genes has been observed in hyphae of an arbuscular mycorrhizal fungus in the presence of 2 × 10–5 M CuSO4 in the laboratory . This suggests that a single driving force can trigger a biological defense mechanism that has multiple purposes. Thus, reduction of toxic cations to native elements may increase as rhizosphere biota fight metal stress and stresses imposed by elevated temperatures expected from global warming.Laboratory evidence has shown that plants , fungi , bacteria , and algae can transform other more easily reducible metals, including Au, Ag, Se , Hg, and Te, to their elemental states both intra and extracellularly. When mechanisms have been proposed, they typically have involved enzymes; however, ascorbic acid was implicated when Hg2+ was transformed to Hg0 in barley leaves . Theoretically all of these metal cations could be transformed by a reducing agent weaker than ascorbic acid . However, binding appears to stabilize cationic forms in the absence of a sufficiently strong reductant such as ascorbic acid. Processes used in materials synthesis that were developed with biochemical knowledge might yield clues to other possible, but presently unknown, biologically mediated reactions in different organisms.The discovery of nanoparticulate copper metal in phytoremediated soil may shed light on the occurrence of copper in peats. Native copper likely forms abiotically in the reducing acidic environments of Cu-rich peat bogs . However, swamps by definition are more oxidizing with neutral to alkaline pHs, and they may be ideal sites for biotic formation of metallic Cu nanoparticles. For example, in swamp peats near Sackville, New Brunswick, Canada, copper species unidentifiable by XRD were dissolved only with corrosive perchloric acid , suggesting they may have been nanoparticulate metal formed by active root systems of swamp plants. If swamp peats evolve to bog peats the Cu reduction mechanism could convert to autocatalysis on the initial nanocrystals . The addition of peats that either act as templating substrates or contain nanoparticulate copper could enhance the effectiveness of using wetlands plants for phytoremediation. In contrast to harvesting hyperaccumulators, the oxygenated rhizosphere would become an economic source of biorecycled copper, and rhizosphere containment would prevent copper from entering the food chain via herbivores,plant pot drainage limiting potential risks to humans.Predicting Cd concentrations in plants is essential for controlling Cd entry into the food chain.

Cadmium uptake by plants is the result of root adsorption to cell walls and of absorption through root cell membranes. Concentration-dependent kinetics performed on seedlings of maize and alpine pennycress allowed short-term Cd uptake by both root uptake pathways to be parameterized . However, the uptake parameters were obtained on plants which were previously cultivated without exposure to Cd. The objective of the present work was to assess how chronic exposure of plants to different Cd levels would affect the root adsorption and absorption rates. Indeed, pre-exposure to metals may substantially modify the kinetics of metal uptake. Stimulation of Cd uptake has been reported to occur in Fe deficient conditions , showing some up-regulation of membrane proteins able to transport Cd. Moreover, Larsson et al. studied the effect of prior Cd2+ exposure on Cd uptake by roots of Arabidopsis thaliana, and found some up-regulation of total Cd uptake in the wild type, and down-regulation in the PC-deficient mutant. Furthermore, very few works have investigated the regulation of root cation exchange capacity by prior exposure to metal. In the present study, we investigated the impact of plant Cd content on root Cd uptake characteristics, at both the cell wall and membrane levels. The experiment was performed on two species with contrasting demand for Cd: a hyper accumulating ecotype of alpine pennycress , well-known for its ability to accumulate high concentrations of Zn and Cd in its shoots, and maize , which retains Cd in its roots. The remaining plants were exposed to a one-hour uptake in a radio-labelled solution in order to assess the absorption rate of Cd according to the level of Cd accumulated during the cultivation. Three Cd concentrations in the radio-labelled solution were used: 0.1 µM, 10 µM and 50 µM. Before immersion of roots in the radio-labelled solution, they were rinsed and exposed to a desorption treatment in order both to minimize contamination of the radio-labelled solution with Cd leakage from the cell walls, and to liberate all exchange sites able to adsorb Cd. For that, each root system was immersed for two hours in 80 ml of buffered solution containing 5 mM of Ca2 and 2 mM MES buffer, then for two further hours in 80 ml of buffered solution containing 0.5 mM of Ca2 and 2 mM MES buffer. After quick rinsing in distilled water, roots were immersed in 650 ml of 109Cd radio-labelled solution containing 0.5 mM CaCl2, 2 mM MES buffer and CdCl2 in the three different concentrations. Root exposure lasted one hour, without significant variation of Cd external concentration. Each root system was then separated from shoots before immersion in successive ice-cold MES-buffered baths containing 2 mM CdCl2 and 5 mM CaCl2. This desorption procedure was interrupted by 2 minutes freezing in liquid nitrogen; roots were then thawed by agitation in a warm desorbing bath, and desorption kinetics went on in ice-cold desorbing solutions for the resulting disrupted root cells . Cadmium collected in the desorbing solutions was quantified through 20 ml samples by gamma-counting .

Cadmium bound to the apoplast at the end of desorption was also quantified through gamma-counting in dry matter. We previously showed that the sudden unloading of metal in the desorption solution caused by the freezing/thawing procedure represents symplastic Cd, while the gradual desorption before and afterwards, corresponds to leakage from the cell walls, regardless of the external concentration . The HATS of maize and alpine pennycress is not affected at all by the low internal accumulation of Cd during growth. The withdrawal of free Cd ion from the cytosol by the complexation with phytochelatins and eventual transport to the vacuole or to the shoots may depress any mechanism regulating the cytosolic Cd concentrations . On the other hand, the plants do not show the same behaviour for the high short-term exposure concentrations: the 0.1 µM Cd contamination of the growth solution would down-regulate the LATS of maize but not that of alpine penny cress, for which some stimulating effect seems to happen. After high Cd accumulation during growth, the Cd symplastic influx is significantly reduced for both plants. Such a diminution of the intracellular uptake of Cd had already been observed on wheat root protoplasts . It may come from down-regulation of the short-time Cd2+ uptake on both high- and low-affinity transport systems. In our study, this reduction of the Cd short-term uptake is higher for the lower exposure concentrations. This supposes that the down-regulation affects the HATS rather than the LATS. The decrease in Cd intracellular influx can also result from up-regulation of the Cd2+ extrusion from intracellular to extracellular space, through PC-Cd efflux , Cd2+/H+ antiport or vesicle excretion . Another alternative explanation to the lower Cd uptake could be the changed appearance of the root system in the Cd-treated plants. Thus, although approximately the same root masses were achieved in all plants tested, the uptake surface might have been different, favoring Cd uptake in the control plants. Finally, some better sequestration of Cd by the cell walls might decrease the entry rate of Cd through cell membranes.

Hydroponic Agriculture: Nurturing Crops in the Absence of Soil

The capabilities of SR FTIR spectromi-croscopy for the direct detection of intracellular biochemical responses to exposures to dilute concentrations of OCs and PAHs will have significant impacts in future research methodology of environmental toxicology.Bio-assays used in aquatic toxicology have taken a prominent position among analytical tests for identifying and measuring environmental hazards. Such bio-assays have been developed for testing a variety of organic and inorganic chemicals, as well as effluents, surface waters and sediment samples for acute and chronic toxicity. Many bio-assays using higher organ-isms such as fish, protozoa and algae have been executed, but are labor- and equipment-intensive, costly and complex. More importantly, these aquatic bio-assays do not provide quantitative information on the impact of pollutants on biological treatment systems. In the view of national and international regulations, regulatory agencies are also supporting the development of new toxicity screening procedures that are sensitive, inexpensive and easier to perform. The use of bacterial in vitro assays such as the Microtox Assay has become an attractive alternative to traditional fish and invertebrate methods for toxicological screening. These new assays have been developed to assess the toxicity of various environmental agents, validated and recognized by several standards organizations. The purpose of this study was to apply selected microbial test protocols to assessing the toxicity of hazardous metals such as cadmium and lead. These metals have been reported to pose a high level of hazard to ecological and human health.A Microtox assay was carried out to measure the relative acute toxicity of metal producing data for the calculation of lead concentration effecting 50% reduction in light output . For each test run, two controls without lead,pot blueberries eight sample/lead dilutions and two replicates were done. Tests were carried out on various percentages of the original lead concentration . The sensitivity of the strain of bio-luminescent bacteria was tested for quality control purposes. Growth and oxygen uptake experiments were performed following previously described protocols.

Descriptive statistics were applied to calculate the means+SD of all data sets associated with specific metal concentrations. Specific growth and oxygen depletion rates were computed as slopes of graphical representations of raw data versus times. The toxic end-points expressed as 50% growth inhibition concentration or as 50% oxygen depletion concentration were next derived from graphical presentations of these specific rates versus metal concentrations. Activity quotients were calculated to determine the degree of toxicity associated with lead exposure. Linear regression analysis was performed to determine the relationship between lead concentrations and the times required for 50% reduction in oxygen uptake .Bioluminescence was used as an endpoint for measuring the effect of Cd and Pb to Vibrio fischeri. For both Cd and Pb, a strong dose-response relationship was determined. The concentrations of Cd and Pb effecting 50% reduction in bioluminescence were computed to be 0.79+0.12 mg/L and 0.34+0.03 mg/L, respectively; indicating that Pb was more toxic than Cd. A strong dose-response relationship was also found in the tests with the mixed population of microorganisms. Figure 1 shows the growth patterns obtained from exposure to lead of the mixed population of microorganisms. Data presented in this figure show an overall increase in bacterial growth with the increase in holding/incubation time. These data also show significant reductions in maximum growths with increasing concentrations of lead. EC50 values were computed to be 4.50+0.04 mg/L, and 3.50+0.02 mg/L for Cd and Pb, respectively. Figure 2 presents the dissolved oxygen uptake rates by the mixed population of microorganisms exposed to various concentrations of lead. In general, curves presented in this figure indicated that individual rates of oxygen uptake decreased as lead concentrations increased. The mean values of EC50 were 5.00+0.42 mg/L for Cd, and 3.80+0.04 mg/L for Pb. These data indicated that the mixed population of microorganisms was about 10 times less sensitive to lead toxicity than the marine bacterium, Vibrio fischeri. Data also showed a strong correlation between TD50s and lead concentrations, indicating a time-response relationship with regard to lead toxicity. A similar result was obtained in experiments with cadmium. Data obtained from this research clearly point out the significance of using microbiological systems for acute toxicity testing in aquatic toxicology. Bio-assays employed in the present investigation fulfilled the requirement criteria of fast toxicity screening based on their simplicity, speed, cost effectiveness and the fact that bacteria grow rapidly, represent a low trophic level, and thus provide sensitive early warning data of environmental impacts at higher trophic levels.

Of the three bio-systems evaluated, the Microtox was the most sensitive; yielding an EC50s that was only about one tenth of values recorded in batch cultures . Although batch systems were time-consuming , and relatively less sensitive than the Microtox, they provided valuable information on the toxic effects of lead on microbial growth and respiration. Also, they were easier to perform, and required less expensive equipment compared to the high cost of the Microtox analyzer. Trinitrotoluene is a munitions chemical that was produced and used on an enormous scale during World Wars I and II in shells, bombs, grenades, demo-lition explosives and propellant compositions. 2,4-Dinitrotoluene , and 2,6-Dinitrotoluene , on the other hand, are used in the manufacture of dyes, in munitions as smokeless propellant powders, and as gelatinizing and plasticizing agents in both commercial and military explosive compositions. Both 2,4-DNT, and 2,6-DNT are produced through denitration of toluene with nitric acid in the presence of concentrated sulfuric acid. Small amounts of DNT isomers also occur as byproducts in the production of TNT. Significant amounts of TNT- and DNT-contain-ing waste waters arising from their preparation and production at Army ammunition plants have been identified in soils, surface water and ground water after leaching from disposal sites. Exposure to TNT and DNTs has been associated with numerous health effects. However, limited scientific information is available regarding the environmental fate, ecotoxicity and health effects of these nitroaromatic compounds. We have performed the Microtox, Mutatox and CAT-Tox assays to determine the acute toxicity, genotoxicity and molecular mechanisms by which these munitions chemicals exert their toxicity. Acute and genotoxicity tests were carried out, using a Microtox/Mutatox Model 500 Toxicity Analyzer System. The Microtox procedure measured the relative acute toxicity of lead, producing data for the calcula-tion of lead concentration effecting 50% reduction in light output . For each test run, two controls without lead, eight samples/chemical dilutions and two replicates were done. The Mutatox Assay was conducted according to the standard test protocol. Nonglowing or dark mutant strains of luminescent bacteria were exposed to the test substance , and the amount of light emitted was measured with the Mutatox Analyzer. The sample-induced reversion from nonglowing to lumi-nescent phenotype was used to indicate the genotoxicity of the sample.

Prepared samples were mixed and preincubated in a water bath at 35 ± 0.5°C for 45 minutes. After preincubation, samples were incubated at 27 ± 5°C for 16, 20 and 24 hours, and the potential genotoxic response of the luminescent bacte-ria was determined at each time period by measuring the light intensity of each cuvette using the Mutatox Model 500 Analyzer. The positive response was defined as the light output of at least two times the light intensity of the reagent control blank. The mammalian Gene Profile Assay was performed for measuring differential gene expression in the human liver hepatoma cell line, HepG2. Thirteen recombinant cell lines and the parental HepG2 Cell line were plated over two 96-well microplates. The cell lines were dosed at five TNT concentrations and incubated at 37°C, 5% CO2, for 48 hours. After the incubation period,square plastic plant pots the total protein was measured by the Bradford method, at 600 nm using a microplate reader. A standard sandwich ELISA was performed and in the final step horseradish peroxidase catalyzed a color change reaction that was measured at 405 nm. The parental HepG2 cell line was dosed in the same manner as the recombinant cell lines, and was used to perform a MTT-based cellular viability assay at 550 nm.Polycyclic aromatic hydrocarbons are a family of compounds that includes some potent car-cinogens that are ubiquitous in the environment. The major metabolic pathway for ingested or inhaled PAHs to water-soluble derivatives is oxidative activation by cytochrome P4501A1 followed by detoxification by phase II enzymes like glutathione S-transferases, especially GSTM1. Interindividual variation in PAH metabolism exists due to genetic polymorphisms in the genes coding for these enzymes. The GSTM1 gene is frequently deleted in individuals, resulting in reduced detoxification. Several single-base changes have been identified in the CYP1A1 gene that appear to result in increased susceptibility to various cancers in these individuals. Because PAHs present a threat to human health, human exposure to PAHs has to be monitored in occu-pational settings. While PAHs consist of hundreds of different aromatic compounds, pyrene is typically present in all of these mixtures. Pyrene is metabolized primarily to 1-hydroxypyrene and detoxified as 1OHP sulfate or glucuronide conjugate and excreted via the urine. Through simple enzymatic methods, these conjugating molecules can be cleaved. Therefore urinary 1OHP is the most commonly used biomarker of exposure to PAHs. Recently, a number of investigators have reported differences in the quantity of urinary PAH metabolites in individuals with poly-morphisms or variations in key enzymes involved in the metabolism of xenobiotics. These findings suggest the need for clarification of the effects of polymor-phisms on the metabolism of pyrene. To investigate the role of these polymorphisms, we have undertaken a study to measure 1OHP levels.Genetic polymorphisms: Peripheral blood lympho-cytes are isolated from the blood samples using Histoprep density separation media . DNA is extracted from the PBLs using standard phenol chloro-form extraction methods. Polymorphisms are analyzed by published procedures: For CYP1A1, the procedure described by Cascorbi et al. is followed.

For identification of CYP1A1 M1, a 899 bp fragment is amplified, then digested with MspI which cuts the variant fragment into a 693 and 206 bp fragment. For the identification of the CYP1A1 M2 polymorphism, a 204 bp DNA fragment is amplified, then subjected to digestion with BsrDI, which cuts the wildtype into a 149 and 55 bp fragment. Restriction enzyme digested PCR products are separated by agarose gel elec-trophoresis. GST analysis is performed using a multiplex PCR that co-amplifies the GSTM1 and GSTT1 genes . An actin DNA frag-ment is co-amplified as an internal control. The absence of a GSTM1 or GSTT1 band in the presence of the actin band indicates a GST gene deletion. Analysis of 1OHP: Methods for analysis of 1OHP follow the protocol by Whiton et al. , which involves overnight enzymatic digestion of all conju-gated forms of pyrene in a 25 ml urine sample, organic extraction of 1OHP, and reverse phase HPLC analysis and quantitation of the 1OHP peak.Inorganic pyrophosphate is an intermediate compound generated by a wide range of metabolic processes, including biosynthesis of various macromolecules such as proteins, DNA, RNA, and polysaccharides. Being a high-energy phosphate compound, PPi can serve as a phosphate donor and energy source, but it can, at high levels, become inhibitory to cellular metabolism. To maintain an optimal PPi level in the cytoplasm, timely degradation of excessive PPi is carried out by two major types of enzymes: soluble inorganic pyrophosphatases and proton-translocating membrane-bound pyrophosphatases. The importance of maintaining an optimal cellular PPi level has been demonstrated in several different organisms. Genetic mutations that lead to the absence of sPPase activity affects cell proliferation in Escherichia coli. In yeast, inorganic pyrophosphatase is indispensable for cell viability because loss of its function results in cell cycle arrest and autophagic cell death associated with impaired NAD+ depletion. In Arabidopsis, a tonoplast-localized proton-pumping pyrophosphatase AVP1 was shown to be the key enzyme for cytosolic PPi metabolism in different cell types of various plants. This enzyme activity has been correlated with the important function that AVP1 plays in many physiological processes. Arabidopsis fugu5 mutants lacking functional AVP1 show elevated levels of cytosolic PPi and display heterotrophic growth defects resulting from the inhibition of gluconeogenesis. This important role in controlling PPi level in plant cells is reinforced by a recent study showing that higher-order mutants defective in both tonoplast and cytosolic pyrophosphatases display much severe phenotypes including plant dwarfism, ectopic starch accumulation, decreased cellulose and callose levels, and structural cell wall defects. Moreover, the tonoplast-localized H+ -PPase AVP1 appears to be a predominant contributor to the regulation of cellular PPi levels because the quadruple knockout mutant lacking cytosolic PPase isoforms ppa1 ppa2 ppa4 ppa5 showed no obvious phenotypes.

Nutrient-Rich Innovation: The Benefits of Hydroponic Crop Production

Nanoceria was found to be non toxic for Danio rerio embryos exposed up to 200 mg l−1 nanoceria during 72 h.Table S1† illustrates the diversity in the measured effect concentration of nanoceria. Even for a given species, the results varied widely between studies. For example, Lee et al. showed significant mortality of D. magna after 96 h of expo-sure to 1 mg l−1 of 15 and 30 nm nanoceria103 while no toxicity was measure in D. magma after the same duration at 10 mg l−1 or a 48 h exposure at 1000 mg l−1 nanoceria.Van Hoecke et al. exposed D. magna to higher concentrations of 14, 20, and 29 nm nanoceria for 21 days, and found an LC50 of approximately 40 mg l−1 for the two smaller particles and 71 mg l−1 for the 29 nm particles.When combining all aquatic toxicity data, including C. elegans , no trends were observed between the nanoparticle size and the toxicity. We observed one extreme value, which is a report of reduction in life span of C. elegans at a concentration of 0.172 μg L−1 . 92 Some have suggested that the toxicity at low concentration can be explained by differences in the aggregation state as a function of concentration. NPs may be less aggregated at lower concentration.105 However, the nanoceria used in this study were positively charged, coated with hexa-methyleneteramine . It is possible that this coating rendered nanoceria much more toxic. Another Fig. 1 depicts the median of the lowest observed effect concentration and the EC10 or LC10 toward different species. This figure illustrates the high variability of the observed LOEC/EC10 between studies for a same organism . Based on the LOEC/EC10, the more sensitive species is the cyanobacte-rium Anabaena, while the least sensitive is Daphnia magna. No toxicity was observed up to 5000 mg Ce/L for the zebrafish Danio rerio and Thamnocephalus platyurus Fig. 1. It is noteworthy that exposure models predict concentrations significantly lower than those for which ecotoxicity investigations have encountered toxic effects. Therefore, nanoceria might not have any impact at environmental concentrations,growing pot despite the fact that some results are more worrying. More-over, most of the nano-ecotoxicology performed on aquatic organisms used a single species or a short trophic links and do not take into account important parameters such as the colloidal destabilization of the nanoceria, their interactions with organic molecules/ particles naturally occurring or bio-excreted, or the flux between compartments of the ecosystems .

To work under more realistic scenario of exposure, few nano-ecotoxicological studies are now performed in aquatic mesocosms with low doses of nanoceria, chronic and long-term exposure. Such studies will allow obtaining reliable exposure and impact data and their integration into an environmental risk assessment model that is currently missing.Although the data on environmental effects are far from complete, it is useful to consider case studies in order to gain knowledge about key data gaps and to give a first impression of relative risks based on current knowledge. While this case study is useful to point out areas where research is most needed, it is critical to point out the limitations of this case study. First, nanoceria have not yet been detected or measured in environmental media, and the actual environmental concentrations are not known. Second, very little is known about the fate and transport of nanoceria in the environment. Third, the toxicity data base is still very limited. Only a select few ecological receptor species have been tested to date and few if any sub-chronic or chronic exposures have been performed in longer lived organisms or in environmentally realistic exposure scenarios. The following case study characterizes the likely exposure concentrations and compares them to toxicity values for soil and water based on emissions due to combustion of fuels containing nanoceria additives and for discharge of chemical mechanical planarization media into sanitary sewers.Based on Table S1,† with the exception of HMT coated nanoceria, which do not apply to this case study and for which coating controls are lacking, the lowest EC10 value measured so far is 8000 ng l−1 for luminescence inhibition in cyano-bacteria.Previous estimates have been made for nanoceria used as a fuel catalyst and arriving in soil and water following atmospheric discharge106 in the UK based on known market size for this product. Clearly there is a wide disparity between concentrations likely to occur due to fuel catalyst combustion106 and the lowest toxicity values observed so far . However, there remains concern that nanoceria may enter water courses through its uses in specialized industrial polishing or chemical/mechanical planarization.Without specialized local knowledge on where these industrial concerns are located, the quantities of nanoceria used, that are disposed of from the premises, and the capacity of the associated sewage treatment plant, the local receiving water concentrations cannot be predicted.

Unfortunately, knowing global or national consumption of nanoceria in the polishing industry would not allow us to predict water concentrations. This is because the use of the product would not be evenly geographically spaced, or linked directly to human population density. However, it is possible to ask: what discharge would be needed to exceed the 8000 ng L−1 toxicity threshold for aquatic exposures? The dilution factor for sewage effluent recommended by EU risk assessment is 10. So effluent would need to contain 80 μg L−1 nanoceria. However, it is estimated that on entering an WWTP 95% of the nanoceria would enter sludge and only 5% pass through into the effluent.In that case the influent concentration would need to be 1.6 mg l−1 nanoceria. WWTPs are designed around population equivalents which tend to be around 160–200 L per PE per day in the UK so a PE unit would need to discharge 256–320 mg Ce per day to receiving waters. Given the current uses of nanoceria, this only seems likely to occur if a large industrial facility is directly discharging wastewater containing high concentrations of nanoceria directly into a sanitary sewer. Note that a population equivalent is a unit describing a given biodegradable load as measured by its biological oxygen demand.We have comprehensively reviewed what is known for nano-ceria about the environmental releases, methods for detection and characterization, fate and transport, toxicity and likelihood of toxicity in soil and water from acute exposures. Initial estimates of releases suggest that the majority of nanoceria will ultimately end up in landfills, with lesser amounts emitted to air, soil and water in that order. Once nanoceria enters the environment, it has been shown that NOM will have a major impact on their fate, transport and toxicity. As with other nanomaterials, aggregation is a key consideration and this has been shown to be influenced by water chemistry and interactions with natural coatings such as NOM. An important feature of nanoceria with respect to its behavior and toxicity is its valence state. There are several techniques that can characterize this property in environmental and bio-logical media, such as XAS, but most require relatively high concentrations. While we didn’t identify studies that detected nanoceria in natural environments or environmental media, a suite of techniques have been used to detect and character-ize them in complex toxicity testing media and in controlled laboratory studies. Thus, a major data gap and area for future research is the prediction and measurement of actual nano-ceria concentrations in the environment, either from point sources or non-point sources.

As a whole nanoceria appears to exhibit similar aquatic toxicity values other commonly studied manufactured nano-materials. For example,square pot a recent review found that species average LC50 values for Ag nanoparticles ranged from 0.01 mg L−1 to 40 mg L−1 while species mean LC50 values for ZnO ranged from 0.1–500 mg L−1 . 116 The range of EC50 values reported for Ce are similar to those for ZnO. Although reported toxicity data here uses LC10 and LOEC values, the range of species means 0.05–25.9 mg L−1 and many of the reported LC50 values are within the range of 0.1–100 mg L−1 , suggesting similar acute toxicity to ZnO NPs in aquatic expo-sures. This is of course based on the available data, which are predominantly on the toxicity of nanoceria to aquatic organisms, with sediment and terrestrial organism data severely lacking. For example, few if any studies have investi-gated toxicity in sediment dwelling organisms, which are likely to be exposed to nanoceria in the aquatic environment due to aggregation, settling and accumulation of nanoceria in sediment. Given the persistence of nanoceria, chronic studies are lacking as we are aware of only the C. elegans study.Equally important, very few species from few taxonomic groups have been tested. Large taxonomic groups such as insects and gastropods have not been tested and only one non-mammalian vertebrate spe-cies has been tested . Another difficulty is that most of the studies were performed with different nano-particles, doses, duration, organisms, exposure media, and their results are not directly comparable. Perhaps due to these differences, there are no apparent patterns to suggest that, as a whole, particle size has a major impact on toxicity. A problem in conducting realistic toxicity studies is the likely transformation of the free particles into homo or hetero-aggregates or even organic complexes in the real environment. There have been few studies that investigated the impact of size across a wide range of systematically varied particle sizes within a single study. Such studies are needed to definitively establish weather size is important. On the other hand coating may be an important variable given the extreme sensitivity seen with HMT coated particles in C. elegans. Coating was demonstrated to be a major determinant of toxicity in a more well controlled study that systematically varied coating properties and used coating controls.2 Of all of the taxonomic groups, toxicity is most well studied in vascular terrestrial plants. Overt phytoxicity of nano-ceria seems minimal and, while root to shoot translocation of these particles is often measurable it is generally quite low. In summary, although the literature on nanoceria impacts on terrestrial plants is not extensive, it is clear that overt phytotoxicity is minimal, even at excessive exposure concentrations. The data do suggest accumulation of nano-ceria within plant tissues, although the precise form of the element that crosses into the plant and the mechanism driving that process remains unknown. The potential trans-generational effects noted in the literature,as well as the complete lack of information on trophic transfer, are areas of concern. In addition, studies investigating environmentally relevant concentrations, potentially secondary effects from nanoceria exposure, including impacts on symbiotic micro-organisms or on edible tissue nutritional quality, certainly warrant further investigation. As a whole, the aquatic and terrestrial toxicity testing data for animals and microorganisms spans multiple orders of magnitude for acute toxicity values . This large variation can be exhibited within a single species exposed to similar nanoceria. For example, toxicity values for D. magna range from around 1–100 mg l−1 for fairly similar particles. Based on the overall toxicity database, it appears that C. elegans is the most sensitive animal and Anabaena is the most sensitive microorganism tested to date, although an important caveat is that the same endpoints were not com-pared across all species and that exposure systems varied. Interestingly no toxicity was observed in the fish species that has been tested even at extremely high exposure concentrations . Unfortunately, only two fish studies have been reported in the literature. There is a complete lack of toxicity testing data for sediment dwelling organisms, and extremely limited data for soil invertebrates. As a whole the data suggest that acute toxicity is possible at low μg L−1 concentrations in the water column. Data are lacking on soils and sediments, but toxicity values are likely to be far lower. One study indicated toxicity at lower concentrations than these values when 8 nm nanoceria were coated with HMT. Since no coating controls were used, it is critical that the influence of this coating and other similar positively charged coatings be studied using a similar end-point and suitable controls. The use and disposal of any nanoceria containing products with this coating should also be evaluated. It is not clear whether the chronic nature of this exposure or the influence of the coating on uptake and toxicity explain why this toxicity threshold is so low.