UC Irvine

Summary: Phytotoxicity of a homologous series of sulphoberaine surfactants, 3‐(alkyldimethyl‐ammonio)‐1‐propanesulphonates, on Brassocattleya orchids increased with increasing alkyl chain length from eight to 14 carbon atoms of the lipophile, levelled off and then declined with the 18 carbon derivative. Because of its high Krafft point the tatter had reduced solubility at the assay temperature. Interfacial tensions of the nutrient solutions, measured against a test lipid, declined m parallel with the observed phytotoxicity. This and previous findings strongly support the suggestion that disruption of cellular membranes by surface active agents plays a key role in their toxicity.