The study consisted of six experiments conducted to examine the spectral response of different varieties of corn (Zea mays), squash (Cucurbita pepo) and bean (Phaseolus vulgaris) under variable zinc (Zn), nitrogen (N) and water treatments. Five of these experiments were conducted in the greenhouse during 1988 and 1989. The sixth experiment was conducted in the field during the summer of 1989. Ground-based, remotely sensed data were collected over plant canopies during the growing period, using an Exotech Model 100 AX hand-held radiometer. The Exotech offers filter sets which match the thematic mapper (TM) bands 1 through 4 (0.45-0.52, 0.52-0.60, 0.63-0.69, and 0.76-0.90 μm). Canopy spectral reflectance and derived vegetation indices showed their ability to significantly discriminate among varieties and variable treatments. Soil adjusted vegetation index (SAVI) mimics the normalized difference vegetation index (NDVI) and transformation normalized difference vegetation index (TNDVI) and exhibited all the characteristics of the NDVI curve when there were no soil influences (a single soil type). Red and near infrared (NIR) reflectance factors exhibited ability in monitoring crop growth and development. The TNDVI showed its superiority in detecting variations and in correlating with ground truth data (biomass cover percent). However, the study showed that remotely sensed data were sensitive to variations (varieties and treatments), but the data did not differentiate between them, unless supported with ground truth data.

F2 progeny from crosses between twenty-seven translocations and eleven genetic characters of Sorghum bicolor (L.) Moench were studied to demonstrate the use and limitations of translocations in mapping genes on chromosomes in this species. A summary of results from 1976 to 1989 is reported using temporary chromosome designation letters A to J. Recombination was estimated between translocation breakpoints and loci for six simply inherited traits. Inferences from linkage data indicate Zbzb to be located on chromosome F; Slsl on chromosome B; Yy (and linkage group 4) on chromosome J; Lglg and Pp (and linkage group 2) on chromosome C; and Bm0, on either A or B. Semisterility of three translocations was found to be linked with genes from two different linkage groups: T-16(FJ) with both Zbzb and Yy; 9157 (BF) with both Zbzb and Slsl; and T-10(CB) with genes Lglg, Pp and Slsl.

Monitoring the nutrient dynamics in the nutrient solutions of hydroponically-grown sweetpotato plants gave the following results. (1) Monitoring the concentrations of critical individual chemical species over time in the hydroponic solution would allow for optimal nutrient management: (a) While the time variation in the Electrical Conductivity (EC) level of a hydroponic solution could suggest normal nutrient uptake, nitrate uptake inhibition, or increased nitrate uptake, the time variation in EC levels could not identify which specific nutrient species were being inhibited or increased in their uptake; (b) Even when the total nitrate assimilation per plant increased over time, the specific nitrate uptake over time actually decreased significantly and correlated well with the saturation of average growth rate, justifying the addition of nitrogen in the solution to achieve optimal growth during the plant's vegetative phase; (c) Doubled-N by ammonium resulted in the significant suppression of the uptake of nitrate and potassium as well as calcium, phosphorus, magnesium, iron and boron, among others; (d) Under doubled-N by nitrate, approximately twice as much nitrate was taken up from the solution relative to the control, indicating that the uptake of nitrate was nitrate-concentration-dependent; (e) Under doubled-N by nitrate, the uptake of potassium was unaffected; and (f) Doubled-K, designed to initiate sweetpotato rooting, significantly suppressed nitrate uptake as desired and kept the potassium uptake unaffected. (2) The fairly reasonable regularity of time variation of EC level and nutrient uptake would allow for mathematical modeling, useful for biomass prediction and stress diagnostics: (a) EC modeling over time by exponential fits resulted in reasonably acceptable r-squares under doubled-N by nitrate treatment and the control condition; (b) EC changes in the standard solution provided reasonable inverse correlation with the plant's average growth rate; (c) Exponential fitting of nitrate concentrations over time resulted in reasonable r-squares both for the doubled-N by nitrate treatment and the control condition; and (d) Under the doubled-K treatment, nitrate uptake was significantly suppressed, so that the resulting variation in nitrate concentration over time deviated significantly from that for the control condition or even that for the doubled-N by nitrate treatment, indicating physiological stress for the plants.

The fungus Verticillium lecanii was assessed for entomopathogenicity against nymphal Bemisia tabaci in an environmental chamber and in a greenhouse mist chamber on the host Euphorbia pulcherima. Proportional mortality of Bemisia nymphs due to fungal exposure were; in the environmental chamber 89-96%, and in the mist chamber 61-89%. Two fungal characteristics, hyphae growth and sporulation, were used as parameters for augmentation experiments. Response to particular honeydew constituents, glutamine, glutamic acid, serine and sucrose in concentrations ranging 500-40,000 ppm were measured. Hyphae growth, in comparison to water agar (1.26-1.52 mm/24 h), was inhibited by all substrates at all concentrations (0.82-1.47 mm/24 h). Sporulation was enhanced at higher concentrations, 17.0-117.0 (x10⁴) spores produced, in comparison with water agar, 10.2-15.5 (x10⁴) spores produced.

The abundance, distribution, and diversity of the soil microbial community from a seawater-irrigated, halophyte agroecosystem was examined. The abundance and trophic composition of decomposers responded to the biochemical composition of residue from three salt-tolerant plants, Salicornia bigelovii, Suaeda sp., and Batis maritima. Decomposers were also influenced by the decomposition environment as it interacted with residue resource quality. The microbial community responded to the availability of residues and the planting density of the halophyte Salicornia bigelovii (Chenopodiaceae) in a season-long study at a research farm in Sonora, Mexico. Soil microbial biomass, activity and efficiency, as well as nematode abundance and trophic composition, generally increased in association with soil-incorporated halophyte residues. However, soil moisture and salinity, which decreased with depth, may also have been influential. Microbial biomass and activity responded to plant density only after plants entered senescence. This result suggested that live-root exudations were not available to the microbial community possibly due to competition with plant roots for available nutrient resources. An increase in the abundance of plant-feeding, but not bacterial- or fungal-feeding, nematodes was associated with the presence of S. bigelovii. The functional diversity of a microbial community from an agronomic halophyte system was compared to natural and constructed halophyte salt marsh communities. Functional diversity of the microbial community at the agronomic sites was intermediate compared to the other sites; e.g., higher than the constructed marsh but lower than the natural salt marshes. Relationships among the study communities determined by microbial functional diversity reflected both habitat and geographical influences.

In jojoba, flower buds are typically produced at every other node on new growth near branch tips. An increase in the number of branch tips (branching frequency) could possibly increase flower bud and fruit production. Studies were conducted to determine the effects of three concentrations of Benzyladenine (BA), Gibberellin4+7 (GA), and Promalin (a mixture of BA and GA) on branching and flower production of three jojoba clones. Treatments involving pinching and untreated control plants were also included. The growth regulators had a significant effect on both branching and flower bud production, and clones differed in their response. For the most responsive clone, the most effective treatments (100 ppm GA and 100 ppm Promalin) resulted in 133% and 110% increase in flower buds after 17 months, respectively. The increase in flower buds was associated with an increase in the number of growing tips and node production. Similar responses were observed in both greenhouse and field experiments. The results of these studies indicate that growth regulators can be used to significantly increase flower bud production on jojoba.

Retractable Roof Greenhouses are a new trend in the greenhouse industry. They allow the improvement of many nursery and crop production practices in semi-arid regions. Hydroponically grown peppers and tomatoes were tested to evaluate possible year-round cultivation in this kind of structure that permits high radiation exposure. Control systems based on radiant surfaces temperatures were developed to integrate, cost effectively, the environmental factors that influence the plants' development and yield, including: air temperature, solar radiation and wind speed. Yields of 7.4 kg m⁻² and 33.0 kg m⁻² were obtained respectively for top quality pepper and tomatoes. These yields were similar or slightly lower than conventional greenhouses in the similar price range and design complexity. This makes the retractable roof greenhouse a mediocre structure for pepper and tomato production in southern Arizona. Radiant surface temperature was found to be a useful parameter for the control of the retractable roof greenhouse climate.

<p> The Riverlands Migratory Bird Sanctuary (1500 ha) was established in 1988 on US Army Corps of Engineers (USACE) land along the Mississippi river in West Alton, Missouri (38.87&deg; N, -90.17&deg; W). It is now cooperatively operated by USACE and the National Audubon Society. About 485 ha consist of actively managed restored bottomland prairie and marshland. The Great Flood of 1993 caused prolonged inundation and destroyed vegetation beds and moist soil plants in the Sanctuary&mdash;an impact still visible today. The goal of this study was to improve plant species diversity and cover, as well as generate more natural vegetation. We employed differing degrees of soil disturbance (tilling and disking) as a means stimulate seed germination from the seed bank. We predicted that the more extreme soil disturbance, tilling, would achieve our goals best. Six replicate marshes within the Sanctuary were chosen for this study. Each marsh was divided into three similarly sized areas and which were randomly assigned one of three treatments: disking, tilling, and control. Vegetative cover and species presence were recorded in 0.25 m² sampling plots at random intervals along each transect in each treatment area. A pre-treatment sample was obtained for comparison. ANOVA of a randomized complete block design revealed strong interactions between marsh (block) and treatment for nearly every community measure. However, marsh effects for cover, species richness, and Shannon diversity were significant beyond this effect. Treatment effects were not significant. Community ordinations by NMDS revealed a strong tendency for plots to aggregate by marsh, not treatment. Preliminary management recommendations can be given based on this study. Restoration activities should focus on site specific characteristics such as the species pool and local hydrology and lean away from immediate additional disturbances. </p>

<p> Nitrate (NO₃^-) leaching from fertilized land can be detrimental to aquatic ecosystems and human health. Although NO₃^- leaching potential is generally found to be low in turfgrass, certain conditions can occur that result in increased leaching loss of nitrogen. Kentucky bluegrass (<i>Poa pratensis</i> L.) is the most widely used cool-season turfgrass species in the temperate and subarctic climate zones in the United States. Due to its popularity, many new cultivars are bred and released each year. Despite the ample amount of information characterizing the agronomic features of Kentucky bluegrass genotypes, little is available documenting their physiological characteristics related to nitrogen use efficiency and how these might affect the NO₃^- leaching potential of the genotypes. Such information would be of great value for both scientists and customers.</p><p> In this comprehensive study, a screening procedure was developed using nutrient solution culture to evaluate differences in NO₃^- uptake among sixty Kentucky bluegrass genotypes. Two cultivars were selected from the sixty to represent genotypes having high vs. low capacity for NO₃^- uptake. These two cultivars were then used to examine the relationship between NO₃^- uptake efficiency and competitiveness for soil nitrogen. Finally, these two cultivars were compared to determine if NO₃^- uptake efficiency affected NO₃^- leaching potential.</p><p> There were significant differences in NO₃^- uptake at both high (1 mM) and low (0.05 mM) N concentrations among sixty Kentucky bluegrass genotypes, with a strong correlation between uptake rates at high and low N concentrations. Julia and Midnight were selected as representing cultivars with efficient and inefficient nitrate uptake, respectively. In nutrient solution culture, Julia exhibited 56% higher NO₃^- uptake rates than Midnight. In a root competition study, in which the root systems of the two cultivars occupied the same soil volume, Julia was more competitive for nitrogen acquisition (absorbed 20 to 71% more NO₃^- ) than Midnight. However, the higher NO₃^- uptake capacity and better competitiveness for soil N in Julia did not result in lower NO₃^- leaching potential. These results suggest that differences in root morphology and architecture may play a more important role than uptake capacity in determining nitrate leaching potential among Kentucky bluegrass genotypes.</p>

<p> Most breeding programs aim at developing superior germplasm and better cultivars that combine high yield, disease and pest resistance, and end-use quality to satisfy the requirements of the growers as well as industry. A population, consisting of 138 F_2-8 recombinant inbred lines (RILs) derived from a cross between 'Steele-ND' and ND 735, was evaluated to study the inheritance pattern of the septoria tritici blotch (STB)-resistant genes, agronomic and quality traits. The genetic map of this population was generated using Diversity Arrays Technology (DArT) (Triticarte Pty. Ltd., Canberra, Australia), a high-throughput genome analysis method. The framework map made of 392 markers, including 28 simple sequence repeat (SSR) markers and 364 DArT markers, spanned a total distance of 1789.3 cM and consisted of 17 linkage groups. The map position of quantitative trait loci (QTL) found in this study coincided with the map position of durable STB resistance genes, Stb1. Thirteen QTL were detected for agronomic and quality traits. More saturation of the current map is needed to explore more QTL for this population.</p>