BIOLOGICAL EFFECTS OF SURFACTANTS .7. GROWTH AND DEVELOPMENT OF BRASSOCATTLEYA (ORCHIDACEAE) SEEDLINGS

Phytotoxicity of a homologous series of sulfobetaine surfactants, 3-(alkyldimethyl-ammonio)-1-propanesulfonates, on Brassocattleya orchids increased with alkyl chain length from 8 to 14 C atoms of the lipophile, levelled off and then declined with the 18-C derivative. Because of its high Krafft point the latter had reduced solubility at the assay temperature. Interfacial tensions of the nutrient solutions, measured against a test lipid, declined in parallel with the observed phytotoxicity. Disruption of cellular membranes by surface active agents apparently plays a key role in their toxicity