EFFECT OF NONIONIC SURFACTANTS ON ETHYLENE RELEASE AND LEAF GROWTH OF PHASEOLUS-VULGARIS L

Effects of three different homologous series of non-ionic surfactants (octylphenolethoxylates, non-ylphenolethoxylates, linear alcoholethoxylates), which are commonly used in formulations of foliar-applied agrochemicals, on ethylene (C2H4) release and growth of primary leaves were investigated in Phaseolus vulgaris L. cultivar 'Processor' plants. Surfactants varied with respect to ethylene oxide (EO) chain length from 3 to 40 mol EO. C2H4 production increased significantly when surfactant concentration exceeded 0.5%; however, the same surfactant (octylphenolethoxylate (OP) with 9.5 mol EO) depressed growth of primary leaves at a concentration as low as 0.01%. C2H4 release was inversely related to EO content of the surfactant molecule. Generally, growth rates of primary leaves were lowest when leaves were treated with surfactants (0.1%) of low to medium EO chain length (3 to 11 EO). The more hydrophilic surfactants (> 20 EO) had the smallest impacts both on C2H4 evolution and leaf growth. The induction of physiological effects and their importance for formulation practice is discussed.