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Title: A NON-LINEAR, DYNAMIC, SIMULATION MODEL FOR XENOBIOTIC TRANSPORT AND WHOLE PLANT ALLOCATION FOLLOWING FOLIAR APPLICATION. III. INFLUENCE OF CHEMICAL PROPERTIES, PLANT CHARACTERISTICS, AND ENVIRONMENTAL PARAMETERS ON XENOBIO

Author
item SATCHIVI, NORBERT - UNIV OF ILLINOIS
item STOLLER, EDWARD - RETIRED USDA EMPLOYEE
item WAX, LOYD
item BRISKIN, DONALD - UNIV OF ILLINOIS

Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: There is a need to predict absorption, translocation and activity of foliar applied pesticides to enhance pesticide efficacy and to develop new products for expression of maximum activity with minimal environmental consequences. We developed a computer model (ERMESSE) that makes such predictions and described its components in a previous paper. In this paper, we test the absorption and translocation of a number of herbicides as influenced by chemical properties, plant characteristics, and environmental conditions. We found that absorption was greater as fat solubility of the herbicides increased, and was least when the herbicides were highly water soluble. However, translocation of the herbicides throughout the plant was greatest when the herbicide properties were intermediate between fat and water solubility. Herbicide absorption decreased as the molar volume of the herbicide and thickness of the leaf cuticle increased; however, herbicide absorption and translocation increased as the relative humidity and air temperature increased. Increases in sugar transport velocity and transpiration rate also increased herbicide translocation rates. The results help to define more closely the effects of various chemical, plant and environmental factors on the absorption, translocation and distribution of herbicides within plants. These findings will be useful to researchers in public and private institutions who develop and design pesticides for maximum biological activity and want to understand all the ramifications for pest management.

Technical Abstract: Computer simulation modeling studies were conducted to examine the influence of xenobiotic chemical properties, plant characteristics, and environmental parameters in determining xenobiotic absorption and translocation. When the effect of the partition coefficient for a xenobiotic was examined it was found that absorption increased as the partition coefficient increased from -5 to 5. On the other hand, xenobiotic translocation from the site of application first increased when the partition coefficient increased from -5 to 2 and then declined with any subsequent increases in the partition coefficient. For xenobiotic compounds considered to be hydrophilic (Log Kow = -2.0), intermediate (Log Kow = 2.0) or hydrophobic (Log Kow = 4.0), variation in the acid dissociation constant (pKa) from 2 to 10 yielded a complex pattern for an effect upon translocation. While it was found that xenobiotic absorption deceased as the molar volume and thickness of the leaf cuticle increased, both xenobiotic absorption and translocation increased as the relative humidity and air temperature increased. Increases in phloem sap velocity and transpiration rate were also found to increase xenobiotic translocation rates. These results are discussed in terms of interactions between chemical parameters for the xenobiotic, characteristics of the plant, and the influence of environmental parameters on xenobiotic absorption and translocation processes.