Enhancement of the Diffusion of Active Ingredients in Barley Leaf Cuticular Wax by Monodisperse Alcohol Ethoxylates

Rates of uptake of active ingredients (ai) across the plant cuticle are enhanced by the action of alcohol ethoxylate (AE) adjuvants. The partitioning of monodisperse AE between aqueous solutions and isolated cuticular wax from barley (Hordeum vulgare L.) leaves was investigated. Quantitative structure−property relationships for wax/water partition coefficients (Kwax/w) and maximum AE concentrations in the wax ( ) were established. In the presence of AE, the diffusion coefficients of six ai in cuticular wax increased by factors of up to 125. AE effects were linearly related to their respective , suggesting a common intrinsic activity. AE had higher effects on the diffusion coefficients of large ai than on those of smaller ones. Conclusions are drawn concerning the mechanism of AE action on the physical structure of cuticular waxes.