A nonlinear dynamic simulation model for xenobiotic transport and whole plant allocation following foliar application. III. Influence of chemical properties, plant characteristics, and environmental parameters on xenobiotic absorption and translocation

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 hydrophilic (log K_ow = -2.0), intermediate (log K_ow = 2.0), or hydrophobic (log K_ow = 4.0), variation in the acid dissociation constant (pK_a) from 2 to 10 yielded a complex pattern for an effect upon translocation. Whereas 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 influence of environmental parameters on xenobiotic absorption and translocation processes.