Foliar uptake of a triethylamine salt of 14C-triclopyr into field bean (Vicia faba L. cv. Maris Bead) leaves was enhanced by the addition of a nonionic organosilicone surfactant, Silwet® L77. The surfactant significantly reduced the surface tension of triclopyr solutions to 22 mN m−1, although improved foliar uptake could not be solely attributed to surface tension changes. Fluorescence microscopy of herbicide solutions containing a fluorescent indicator showed that addition of Silwet L77 permitted these solutions to penetrate rapidly into the stomatal pores on the adaxial surface of the bean leaf.

A model of the uptake process for triclopyr and the modifications induced by Silwet L77 has been established. The model assists in determining the mode of action of Silwet L77 and can be used in interpreting the action of other organosilicone surfactants.