ABSTRACT
A series of ethoxylated nonylphenol surfactants with varying chain lengths (n = 6 to 30) was studied in terms of their influence on the penetration and transport of systemic fungicides in plants. Surfactants play an important role in the penetration and transport processes at the different barriers of the plant: the epicuticular wax layer, the cuticle, and the cell membranes. On the leaf surface they can modify the physical form of the deposit. In this way lipophilic surfactants with short ethylene oxide (EO) chains may improve leaf uptake. They also penetrate the epicuticular wax layer and disturb the penetration of the fungicides. This interference is dependent on the surfactant concentration and is related to the formation of micelles. The transcuticular penetration of the fungicide is enhanced by the presence of higher concentrations of hydrophobic surfactants. Because surfactants have only a limited penetrability in plants their influence is restricted to the outer cell layers. Their role in cell membrane permeability is limited even though it can be demonstrated that they cause severe cell membrane disruption and thereby influence the penetration of fungicides into the plants.
