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Yuan-Hai Zhang and Lyle E. Craker

Air pollution may play a role in gametophytic selection. To estimate whether such selection was occurring, pollen grains from homozygous and heterozygous tomato plants were tested under pollution stress. Homozygous pollen could be expected to respond to pollution more uniformly than heterozygous due to the identical genotype of the pollen grains. Acid rain reduced pollen germination and tube elongation in Lycopersicon hirsutum LA1777 (heterozygous) and Lycopersicon pennellii LA716 (nearly homozygous). UV-B reduced tube length of the pollen from both plants, but ozone only reduced pollen tube length of L. pennellii. The responses of these two kinds of pollen to acid rain, ozone, and UV-B appears to be same in terms of heterozygosity and stress dosages, suggesting the reduction of pollen germination and tube elongation under pollution stress may be mediated through physiological or physical alterations and not a response of different genotypes.

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Joyce G. Latimer, Reuben B. Beverly, Carol D. Robacker, Orville M. Lindstrom, S. Kristine Braman, Ronald D. Oetting, Denise L. Olson, Paul A. Thomas, Jerry T. Walker, Beverly Sparks, John M. Ruter, Wojciech Florkowski, Melvin P. Garber, and William G. Hudson

partial funding from the Pollution Prevention Assistance Division of the Georgia Department of Natural Resources.

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Joyce G. Latimer, Reuben B. Beverly, Carol D. Robacker, Orville M. Lindstrom, Ronald D. Oetting, Denise L. Olson, S. Kristine Braman, Paul A. Thomas, John R. Allison, Wojciech Florkowski, John M. Ruter, Jerry T. Walker, Melvin P. Garber, and William G. Hudson

partial funding from the Pollution Prevention Assistance Division of the Georgia Department of Natural Resources.

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Huiying Li, Hongji Luo, Deying Li, Tao Hu, and Jinmin Fu

Heavy metal pollution is a worldwide ecological problem because of its impact on plants and animals and ultimately on the health of human beings via the food chain. Lead is one of the most abundant and widely distributed heavy metals because of its

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Lee S. Altier, R. Richard Lowrance, and R.G. Williams

Even with careful management, within-field practices are often insufficient to prevent considerable nonpoint source pollution to adjacent streams. Water resources suffer from sediment, N, and P transported in surface runoff and N in subsurface movement when fields are cultivated up to stream banks. The maintainance of forested buffer systems between farmland and streams has been proposed as a remedy for mitigating pollution. Chemical movement through such a buffer system has been monitored for several years at the University of Georgia Coastal Plain Experiment Station. With the aid of that data, the Riparian Ecosystem Management Model is being developed to simulate biological, chemical, and hydrologic processes in order to evaluate the effectiveness of buffer system management for reducing the influx of pollutants to streams. The model allows an examination of the long-term potential of a buffer system under changing environmental conditions.

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Dan J. Pantone and Robert A. Young

Nonpoint-source pesticide pollution from horticultural and other agricultural activities is a primary factor determining the quality of surface water. A menu-driven, interactive pesticide transport submodel has been developed for the agricultural nonpoint-source (AGNPS) pollution model. AGNPS simulates the surface transport of pesticides, sediment, and water from the headwaters to the outlet in a stepwise manner so that an assessment can be made at any point within a watershed boundary. The model can be used by farmers, agricultural extension agents, agrichemical industry workers, or researchers to develop agricultural activities that minimize the surface transport of pesticides. This user-friendly pesticide transport model is available at no cost to users through the Internet.

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W.A. Retzlaff, W.W. Barnett, L.E. Williams, and T.M. DeJong

Japanese plum (Prunus salicina Lindel. `Casselman') trees exposed to three atmospheric ozone partial pressure treatments were sprayed with a summer application of Volck Supreme oil (1% aqueous solution) to control an outbreak of spider mites (Tetranychus spp.). Phytotoxic effects were observed on the foliage of trees in the plots exposed to ambient or higher atmospheric ozone partial pressures 5 days following spray application. Foliage on trees exposed to 0.044 and 0.081 μPa·Pa-1 ozone [12-h mean (8 Apr. to 12 June 1992)] partial pressures developed water spotting and more foliage abscission than trees exposed to charcoal-filtered air (0.024 μPa·Pa-1 ozone). Thus, ozone air-pollution stress may predispose plants to increased phytotoxicity from summer oils.

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Dan James Pantone and Robert A. Young

A pesticide transport submodel has been incorporated into a distributed parameter simulation model. AGNPS (AGricultural NonPoint Source Pollution Model) can evaluate the effect of agricultural pollution sources on surface runoff. Six pesticide classes are used: herbicides, insecticides, fungicides, nematicides, plant growth regulators, and desiccants/defoliants. User inputs for the model include the time of pesticide application (preplant, preemergence, or postemergence), application rate, application efficiency, percent canopy cover, soil and foliar pesticide residues, soil and foliar pesticide decay, water solubility, foliar washoff threshold and fraction, incorporation depth and efficiency, and sorption coefficient. Areas of pesticide losses and accumulations are indicated in tabular and graphical outputs. Alternative management practices can be simulated, and therefore assist in the optimization of practices to reduce pesticide runoff.

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Atilla B. Goknur and Theodore W. Tibbitts

The magnitude of dark opening of stomata on leaves of Irish potato (Solanum tuberosum L.) was studied to determine if this opening was related to the high sensitivity of these plants to air pollutants. Stomatal opening was studied over diurnal periods both in the field and in controlled environments. In both environments, stomatal conductance decreased rapidly at the initiation of dark to 0.1 cm·s-1 but then increased to 0.2 cm·s-1 over the dark period. However conductance was always less in the dark than in the light (0.3 to 0.9 cm·s-1). During the early part of the dark period, stomatal conductance in controlled environments was not as great as in the field, but conductance was similar in both environments over the latter part of the dark period. Cultivars Norchip and Kennebec had smaller conductances during the first hours of the dark than Haig or Katahdin, and all cultivars increased in conductance over the dark period. `Haig' showed slightly higher conductance than the other three during the last 4 hours of the dark period. Injury to `Haig' from 3-hour fumigations with sulfur dioxide (SO2) or ozone (O3) demonstrated that exposures during the day generally produced more injury than during the night, although exposures with SO2 during the last 3 hours of the light period produced similar injury to exposures at the end of the dark period. Thus, although partial opening during the dark may be permitting some pollution injury, it is concluded that previous published reports of similar opening of stomata on Irish potatoes during the light and dark periods, and equal or greater pollution injury during the dark compared with the light period, were not substantiated and apparently resulted from procedural artifacts.

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W. Voogt

In the Netherlands, many crops in protected cultivation changed from soil to soilless culture in recent years. The reasons for this development were problems with soil sterilization and better growth control with soilless culture, which led to considerable yield increases. However, the growing systems used, with free leachate drainage, contribute highly to pollution of the ground and surface water with minerals (N and P). To reduce this emission, closed growing systems were developed, i.e., systems with recirculating nutrient solutions. Inherent to these systems, however, were problems such as the rapid spread of pathogens in the root environment. Methods were developed for disinfestation of the nutrient solution. Salt accumulation was also a concern, the concentrations of ions in the water used for closed systems must be lower than the uptake capacity of the plants. To avoid depletion and accumulation of certain nutrients. the addition of nutrients should be adapted to the demand during the cropping period. For this purpose, nutrient solutions and guidelines for adjustments during the cropping period were developed for several crops.