Phloem Mobility of Xenobiotics. VII. The Design of Phloem Systemic Pesticides

Abstract

We have developed a mathematical model for the plant vascular system that enables the prediction of a compound's phloem systemicity as a function of its partition coefficients and acid dissociation constants. The mathematical model can account for the sensitivity of systemicity to plant parameters such as plant size and pH of the phloem sap. This paper reviews this model and demonstrates how it accounts for the phloem systemic properties of most herbicides as well as that of many endogenous substances such as plant hormones. The model also can be used to design phloem systemic pesticides as illustrated for a pronematicide that successfully controls nematodes when applied foliarly to transgenic tobacco plants capable of regenerating the parent nematicide in a root specific fashion.

Vectorizing agrochemicals: enhancing bioavailability via carrier‐mediated transport

“…Therefore, the mechanism of membrane permeation is a key factor for both the long‐distance transport and distribution of agrochemicals in plants. Phloem mobile insecticides and fungicides have been proposed to be efficient in controlling piercing and sucking insects, especially if they attack the root system and the shoot, as well as root and vascular pathogens . However, only a limited number of current insecticides and fungicides exhibit a high phloem systemicity, e.g.…”

Selecting the right compounds for screening: does Lipinski's Rule of 5 for pharmaceuticals apply to agrochemicals?

“…The barriers to uptake which crop‐protection chemicals must cross vary. Post‐emergence herbicides must generally be able to penetrate the leaf cuticle35, 36 to have whole‐plant activity, and often have superior properties when they are phloem‐mobile 37–42. Uptake through the leaf cuticle is somewhat analogous to trans‐dermal delivery of drugs,43 since both the leaf cuticle and the skin mainly protect the organism from the external environment by preventing water loss and excluding exogenous chemicals.…”

Synthesis of Rotenone-O-monosaccharide Derivatives and Their Phloem Mobility

“…Prediction of phloem mobility of the tested compounds (3a−3f, rotenone and dalpanol) using the Kleier model. 30 Log K o/w and pK a in Table 2. rot = rotenone; dal = dalpanol.…”