This is particularly restrictive for horticultural crops, in which many varieties are required to meet different seasonal production requirements and diverse consumer preferences, and any single variety has a relatively small market share. For example, dozens of different types and varieties of lettuce are grown throughout the year as production shifts between summer and winter locations in California, Arizona and Florida. Some agronomic seed companies budget $50 million for the full commercialization of a new biotech crop, in addition to the standard costs for developing and marketing a traditional variety. Given the small acreage of horticultural crops and their much lower overall value, it is difficult to justify the investment in transgenic horticultural crops. For example, the total U.S. market for iceberg lettuce seed is about $27 million. A typical single variety is worth about $150,000 to $250,000 during its 5-year market lifetime, which suggests that garnering a large market share of lettuce varieties with significant added value would be necessary in order to pay for the additional costs imposed on biotech varieties.Despite this gloomy picture, regulatory strategies may be possible that would protect public and environmental safety while decreasing the cost of introducing biotech specialty crops . Plant breeding companies employing biotechnology can manage and reduce regulatory costs by carefully and deliberately determining the necessary testing requirements. Costs can be reduced by focusing development on biotech genes that have already been commercialized in agronomic crops, since expensive toxicity studies done on a new protein produced in a biotech agronomic crop can be used for the same protein produced in a biotech horticultural crop.

The USDA IR-4 program conducts and pays for the collection of efficacy and safety data on pest-control chemicals for “minor” or “specialty” crops, which include most horticultural crops . A new,vertical farm expanded “biotech IR-4” program focused on full crop registration, including EPA, USDA and FDA requirements, could benefit horticultural crops being developed in universities, government laboratories and small companies. This is particularly critical for the next generation of transgenic products, which will be more consumer-oriented and specific to horticultural crops. Because horticultural products in the pipeline are likely to have altered nutritional or quality traits, specific safety tests will be required that cannot rely on data generated for agronomic crops. Without a program like IR-4, testing requirements could preclude such products from ever being developed and reaching the market. As demonstrated by Calgene and Zeneca with their early tomato products, consumers are receptive to labeled products that have clear quality or price benefits. However, focusing entirely on consumer-oriented traits would forgo valuable benefits for crop production, such as virus resistance, which could have enormous advantages for producers that would not be readily recognized by consumers. As further experience is gained with biotech methods, regulatory requirements should be relaxed for categories of products posing little health or environmental risk. In addition, generic crop and gene approvals , rather than the current “event-specific” approach , would do much to encourage further development of such products. Around the world, farmers desire and in some cases demand the benefits that can come from the improved varieties. In India, for example, extensive precommercialization field trials of insect-resistant cotton found average yield increases of 80% along with a 68% reduction in insecticide use . Farmers saw the value of the varieties and grew 25,000 acres of insect-resistant cotton in 2001, prior to government approval .

Similarly, a significant percentage of soybeans in Brazil was grown from herbicide-resistant seeds smuggled into the country from Argentina and propagated by farmers, as Brazilian courts held up their release despite governmental approval. While planting of insect-resistant corn has not been approved in Mexico, Mexican workers returning from the United States have brought back seed corn for planting, and biotech food grain sold in Mexico has also been planted. At the 2002 Institute of Food Technologists’ annual meeting, E.C.D. Todd of Michigan State University reported that Thai farmers are smuggling and planting biotech seeds from China. While the distribution of biotech varieties outside of legal channels cannot be condoned, these examples illustrate that farmers are aware of the advantages these varieties can deliver. As research continues at many companies, universities and government laboratories, biotech horticultural products having similar attractions for growers and consumers may overcome the current financial and logistical hurdles facing their commercial development.Despite vocal opposition, agricultural biotechnology continues to advance. China has made significant strides in commercializing GE horticultural crops over the past 10 years and may well become the world’s leader during the next 10 years . China was the first country to commercialize biotech plants, beginning with field production of thousands of acres of virus-resistant tobacco in 1988, followed by virus-resistant tomatoes and sweet pepper in 1994 . In the mid-1990s, China was criticized by an American delegation for having only a provincial and not a national product-approval system. For several years afterward, it was difficult to determine whether further commercial plantings of biotech crops occurred in China . Interestingly, China established 1997 as the “official” commercialization date for biotech cotton, tomato, sweet pepper and petunia, which is when the crops were authorized by the agricultural-biotechnology safety office of the Chinese Ministry of Agriculture .

China currently claims to be second only to the United States in agricultural biotech research, development and cultivation, and China is taking full advantage of uncertainty caused by the European Union’s stance on biotech approvals. Beijing University vice president Chen stated, “I expect that in 10 years between 30% and 80% of the rice, wheat, maize, soya, cotton and oil seed crops in China will be transgenic crops. We can take advantage of this 4-year halt [E.U. moratorium] to turn China into a world power in genetically modified organisms.” China is in an excellent position to develop and create internal markets for biotech horticultural crops and clearly has the opportunity to surpass the United States in biotech crop development. Recently, China erected barriers to the importation of biotech grains, creating confusion for U.S. and world exporters, while backing away from some of its earliest commercial biotech products . It is not known whether this is due to internal concern over biotech products or fear of jeopardizing its own export markets to Europe, or is a trade barrier to allow for additional internal development of biotech products. Greater clarity will occur should this issue come before the World Trade Organization . Regulatory issues and costs are reducing commercial opportunities for new biotech crops in the United States. Of course, China will need to meet the requirements of any country receiving their exports,nft vertical farming but currently it is unclear whether any of China’s biotech products are being exported. Korea and Japan are not likely to press this as a trade issue. Other internal political issues are currently complicating commercialization efforts within China, but these are likely to be only short-term barriers . While the United States falters over biotech fruits and vegetables, China is positioning itself to be the world leader in coming years. For the American horticultural industry, the results could be devastating if the United States loses its current competitive edge and more agricultural production moves overseas.Most plants obtain the majority of their nitrogen through root absorption of NH4 + and NO3 – ions from the soil solution. Roots are thought to assimilate most of the NH4 + near the site of absorption to avoid accumulating the high amounts of free NH4 + that would dissipate the transmembrane proton gradients required for respiratory electron transport and for sequestering metabolites in the vacuole . In contrast, plants can store high concentrations of NO3 – in their tissues without toxic effect and may translocate a large portion of this NO3 – to the shoots . The chemical form of the nitrogen source, NH4 + or NO3 – , influences a myriad of plant processes including responses to CO2 enrichment , and each source elicits distinct patterns of gene expression . Nonetheless, characteristics of the root apex under exposure to physiological levels of NH4 + or NO3 – have received relatively little attention. A previously published study profiled net fluxes of NH4 + , NO3 – , and H+ along the axis of the seminal root in a maize seedling . Local influx was measured by depletion of nitrogen from the bathing solution surrounding the root. When nitrogen was supplied as NH4NO3, net influx of NH4 + was rather uniform through the root cap and root growth zone, When nitrogen was supplied as Ca2, the pattern of nitrogen influx was significantly different: net NO3 – influx increased from 1.5 nmol mm 1 h 1 in the root cap to much higher values, 5.4 and 7.6 nmol mm 1 h 1 at 3.5 and 11 mm, respectively, from the root apex.

The presence of NH4 + inhibited net NO3 – influx. This inhibition together with the observed pattern of H+ fluxes indicated that the entire maizeroot apex absorbed more exogenous NH4 + than NO3 – when both forms were present in the medium. The approach in this study is to compare endogenous ‘deposition rates’ of NH4 + and NO3 – with the values for net influx of the exogenously supplied nitrogen forms reported in the earlier study. This leads to an understanding of the source and sink relationships for nitrogen in the growing root. Deposition rates are defined to be the net rate at which a nutrient is added to or removed from the local tissue element. These rates can be calculated from data on tissue concentration and growth velocity . This kinematic approach has illuminated physiology in a number of studies of plant–environment interactions . Here, the spatial profiles of the nitrogen concentrations provide information about metabolic function. Moreover, comparison of net deposition to exogenous influx shows whether the net import or export is occurring at a particular location. Finally, this study extends the approach to show the total uptake of nitrogen into a tissue element during its expansion and displacement. In the following experiments, maize roots were exposed to a nutrient solution that contained NH4 + or NO3 – as sole N sources, both forms together, or no N source. The concentration of NH4 + or NO3 – in the solutions containing them was 0.1 eq m 3 N, a level consistent with those found in soil solutions . Net deposition rates of NH4 + and NO3 – were calculated and root contents of NH4 + and NO3 – and other solutes were measured along the root axis from the apex to 60 mm and in the xylem sap to assess the relative contributions of NH4 + and NO3 – both to the N budget and to the osmolarity in the apical 60 mm, including the 10 mm that comprised the elongation zone.Individual seedling roots were gently blotted dry before they were rapidly frozen on a thermoelectric cold-plate mounted under a dissecting microscope. Axial sections of 1-mm length were made with a fine razor at 1-mm increments from 1 to 10 mm and at 20, 40, and 60 mm from the apex along each of 10 roots. Root sections from each location were pooled. Root sections pooled from 10 roots were weighed to estimate fresh mass and then oven dried at 50  C and weighed to estimate dry mass. Root sections from another 10 roots were placed directly into the sample chamber of a Wescor 5100 Thermocouple Psychrometer to assess osmolarity. Potassium was extracted from sections from a different 10 roots with a solution of 2% acetic acid and analysed using atomic emission spectrometry . Soluble carbohydrates were extracted with boiling water and analysed via HPLC with mass selective detection . Organic acids were extracted with 80% ethanol solution, evaporated under nitrogen at 50  C, redissolved in 0.1 M H2SO4 plus 0.05% EDTA, and analysed via HPLC with UV detection at 195 and 245 nm . Lastly, sections from 10 other roots were collected in Eppendorf tubes containing 1.5 ml of 1 mol m 3 CaSO4, which was adjusted to pH 3 with H2SO4, sonicated for 30 min, and centrifuged.For each N-treatment, there were three or four replicates of sections pooled from 10 roots each for osmolarity, two replicates for potassium, two for soluble carbohydrates, one for organic acids, and at least three for NH4 + and NO3 – .