Phototoxicity of selected non-ionic surfactants to soybean Glycine max cell suspensions

Abstract

The phytotoxicity of a series of linear alcohol ethylene oxide adduct non-ionic surfactants to achlorophyllous soybean Glycine max (L.) Merr. var. Wilkin cell suspensions was determined. The compounds tested were 1-dodecanol (12-0), four of its ethylene oxide (EO) adducts, and an adduct of 1-decanol with 6·7 (average) EO units (10- 6·7 ). Three of the dodecanol adducts were homogeneous surfactant preparations with 2,6 or 8 EO (12-2, 12-6, 12-8, respectively) and one had an average of 17 EO (12- 17 ). The 12-0 compound had no effect on cell growth. Its lipophilic EO adducts 12-2 and 12-6 stimulated growth slightly (less than 30%) at the lower concentrations (22 to 55 μ m and 7 to 26 μ m, respectively) 8 days after treatment. All compounds except 12-0 inhibited growth at the higher concentrations (ranging from 11 to 120 μ m, depending on the compound). Growth inhibition by these adducts increased with EO chain length from 12-2 to 12-8 and then decreased for the very hydrophilic 12- 17 . Growth was only slowed by surfactant treatments at intermediate concentrations and eventually the cells attained nearly the same maximum dry weight as untreated cells. The 10- 6·7 surfactant affected the cultures similarly, but not identically, to the 12-6 and 12-8 surfactants. The surface tensions of the treating solutions were measured. The concentrations of 12-6, 12-8, 12- 17 and 10- 6·7 at which phytotoxicity occurred were too low for micelle formation.