Surfactants markedly increased the uptake of picloram by Eucalyptus viminalis and E. poly-anthemos 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.