PHLOEM MOBILITY OF XENOBIOTICS .7. THE DESIGN OF PHLOEM SYSTEMIC PESTICIDES

We have developed a mathematical model for the plant vascular system t hat enables the prediction of a compound's phloem systemicity as a fun ction of its partition coefficients and acid dissociation constants. T he mathematical model can account for the sensitivity of systemicity t o plant parameters such as plant size and pH of the phloem sap, This p aper reviews this model and demonstrates how it accounts for the phloe m systemic properties of most herbicides as well as that of many endog enous substances such as plant hormones. The model also can be used to design phloem systemic pesticides as illustrated for a pro-nematicide that successfully controls nematodes when applied foliarly to transge nic tobacco plants capable of regenerating the parent nematicide in a root specific fashion.