An investigation was carried out to determine the fate and persistence of fenitrothion (0,0-dimethyl-0-(3-methyl-4-nitrophenyl)-phosphorothioate), applied to four year old seedlings of balsam fir, white spruce, and Jack pine under greenhouse conditions. The insecticide disappeared rapidly from the surface of conifer tissue while the absorbed residues were more persistent. Greater absorption of the pesticide was coupled with increasing persistence in pine, spruce and fir. An in vitro study carried out on glass surfaces demonstrated that rapid disappearance of the pesticide was primarily due to volatilization. TLC analysis of the conifer extracts was consistent with this dissipation mechanism since 14C-ring degradation products were present for the most part only in trace amounts. Autoradiographic tracing studies demonstrated the ability of 14C-fenitrothion to be transported acropetally into the young foliage of fir, and to a lesser extent in spruce. That this took place via the xylem (apoplastic transport) was confirmed by histoautoradiography. These results were taken as evidence for the systemic potential of fenitrothion for budworm control.

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<p> The greenhouse industry is interested in light emitting diodes (LEDs) as a light source supplement to solar light to improve plant growth and development. Before LEDs can be adopted as supplemental light for greenhouse crops, plant responses to LED spectral quality need to be investigated. Tomato and cucumber seedlings were grown under different supplemental blue and red photon flux ratios (B:R ratios) under high (16-19 mol m^&ndash;2 d^&ndash;1) and low (5-9 mol m^&ndash;2 d^&ndash;1) solar daily light integrals (DLIs). The supplemental daily light integral was 3.6 mol m^&ndash;2 d^&ndash;1. A treatment without supplemental light served as a control. Both tomato and cucumber seedlings had increased growth rate and improved morphology when grown under the supplemental LED light compared to the control. However, no significant differences were observed for any growth and morphological parameters measured in this study between the different B:R ratios for both cucumber and tomato transplants under high DLI conditions. Cucumber seedlings showed a tendency to decrease dry mass, leaf number and leaf area under low DLI conditions with increasing B:R ratio. Tomato seedlings did not show any differences between the different B:R ratios under low DLI conditions. Seedlings growth and morphology under supplemental LED light were compared to those under supplemental high pressure sodium (HPS) light. Cucumber seedlings under supplemental HPS light had greater shoot dry mass than those under the supplemental red LED light. Tomato shoot dry mass showed no differences between the HPS and red LED supplemental light treatments. Cucumber seedlings were also grown under supplemental LED pulsed lighting and supplemental LED continuous lighting. Cucumber seedlings showed no differences in shoot dry mass and net photosynthetic rate between the treatments. Collectively, these studies concluded that red LED is preferred for supplemental lighting and the increase of blue light does not offer any benefits unless the efficiency of blue LEDs largely exceeds the red LEDs. The results of this research can be used for fixture development by LED manufactures and as a decision making tool for the adoption of supplemental LED lighting by greenhouse growers.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7039. Adviser: Thomas W. Fermanian. Includes bibliographical references (leaves 165-180) Available on microfilm from Pro Quest Information and Learning.

<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>