Evidence for Surfactant Solubilization of Plant Epicuticular Wax

The solubilization of isolated, reconstituted tomato (Lycopersicon esculentum Mill.) fruit and broccoli (Brassica oleracaea var. botrytis L.) leaf epicuticular waxes (ECW) by nonionic octylphenoxypolyethoxy ethanol surfactant (Triton X-100) was demonstrated in a model system by TLC and fluorescence analysis using pyrene as a fluorescent probe. ECW was solubilized at or above the surfactant critical micelle concentration; solubilization increased with an increase in micelle concentration. As shown by the fluorescence quenching of pyrene, surfactant solubilization of the ECW increased rapidly for the first 12 h, then approached a plateau, increased linearly with an increase in temperature (22−32 °C), and decreased linearly with the log of the polyoxyethylene chain length (range 5−40 oxyethylenes). These data are discussed in relation to surfactant effects on phytotoxicity and performance of foliar spray application of agrochemicals. Keywords: Cuticular penetration; micelles; fluorescence quenching; tomato; Triton X-100; Lycopersicon esculentum; Brassica oleracea; broccoli