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Interaction of Surfactants with Plant Cuticles

Published online by Cambridge University Press:  20 January 2017

F. Dan Hess
Affiliation:
AffyAgro Unit of Affymax Research Institute, 3410 Central Expressway, Santa Clara, CA 95051-0703
Chester L. Foy*
Affiliation:
Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, 502 Price Hall, Blacksburg, VA 24061-0331
*
Corresponding author's E-mail: cfoy@vt.edu.

Abstract

How surfactants modify the characteristics of a spray liquid is now reasonably well understood. Beneficial effects are primarily associated with reduction in surface tension. However, the mechanisms whereby surfactants enhance the diffusion of herbicides across the plant cuticle are less clear. Generally, hydrophilic surfactants with a high hydrophile/lipophile balance (HLB) are most effective at enhancing penetration of herbicides with high water solubility, whereas lipophilic surfactants with a low HLB are most effective for enhancing uptake of herbicides with low water solubility. Both high- and low-HLB surfactants are absorbed into the cuticle, but current theory suggests different mechanisms are involved in enhancing diffusion of hydrophilic and lipophilic herbicides across the cuticle. Surfactants having a high HLB are absorbed into the cuticle and enhance the water-holding capacity (hydration state) of the cuticle. With increased cuticle hydration, the permeance of hydrophilic herbicides into the cuticle is increased, which increases the herbicide diffusion rate at a constant concentration gradient. Surfactants having a low HLB are absorbed into the cuticle and increase the fluidity of waxes, as measured by a small reduction in melting point. This increased fluidity increases the permeance of lipophilic herbicides in the cuticle, which, in turn, increases their diffusion rate at a set concentration gradient.

Information

Type
Symposium
Copyright
Copyright © Weed Science Society of America 

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