A physiological study of the effects of triton surfactants on Lemna minor L.

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Abstract
Adjuvants significantly contribute to many commercial herbicide/pesticide formulations and are often present at concentrations approaching those of the active ingredient. The Canadian Forest Service is currently testing alkyl aryl polyether alcohol adjuvants as “acceptable” replacement surfactants in the fenitrothion formulation used to control the spruce budworm, Choristoneura fumiferana. This study describes the toxic effects of these compounds on a common and widespread aquatic vascular plant, Lemna minor L.The parameters monitored during the 14‐d exposure included growth (biomass), frond fluorescence and chlorophyll content, conductivity of the test media and specific ion leakage. At 1 μg/ml, no response of any of the monitored parameters was observed for any of the Tritons, and 10 μg/ml resulted in no response for Triton X‐114. Exposure to 10 μg/ml of the other Tritons tested, however, resulted in toxic effects such that frond development was depressed 25 to 50%. Exposure to 50 μg/ml of the lower ethoxylates, Tritons X‐l5 and X‐35, elicited approximately twofold greater depression of the parameters assessed than did treatments with comparable concentrations of the higher ethoxylates, Tritons X‐100 and X‐114. A positive correlation was obtained between the degree of phytotoxicity and the hydrophilie‐lipophilic balance (HLB), and partition coefficients for the Triton surfactants.