Uptake of picloram by eucalypt leaf discs. I. Effect of surfactants and nature of the leaf surfaces

Surfactants markedly increased the uptake of picloram by Eucalyptus viminalis and E. polyanthemos leaf discs. The effects of different surfactants and different surfactant concentrations on uptake depended largely on the degree of wetting by the applied solution on the leaf surface. A species-surfactant interaction was evident with some surfactants, and this was examined in terms of differences in leaf-surface characteristics between the two species. The effects of surfactants on the leaf surfaces were also observed. The inadequacy of surface tension as a measure of the ability of a solution to wet leaves, and to stimulate herbicide uptake, is discussed.