PHLOEM MOBILITY OF XENOBIOTICS .5. STRUCTURAL REQUIREMENTS FOR PHLOEM-SYSTEMIC PESTICIDES

Remote and relatively inaccessible parts of plants such as roots and meristematic tissue can readily be reached by foliar-applied xenobiotics if the latter are capable of entering into and moving in the phloem. Development of a passive transport model provides a description of the time course of this movement and its dependence upon the physical properties of the chemical and the condition of the plant vascular system. The model so developed is used to formulate principles for rendering otherwise non-systemic xenobiotics phloem-mobile. These principles can be categorized according to the nature of the chemical modifications that facilitate phloem translocation. These modifications include (a) sugar conjugation, (b) acid functionalization, and (c) formation of quaternary salts from basic parents. The potential of these modifications to facilitate the phloem translocation of a wide range of pesticides is discussed.