ACCUMULATION OF PHYTOALEXINS IN COTYLEDONS OF FRENCH BEAN (PHASEOLUS VULGARIS L.) FOLLOWING TREATMENT WITH TRITON (T‐OCTYLPHENOL POLYETHOXYETHANOL) SURFACTANTS

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Abstract
Triton surfactants induced accumulation of phytoalexins in cotyledons of the French bean. The degree of accumulation was related to the phytotoxicity of the surfactant, which was dependant upon the length of the polyethoxyethanol side chain. Triton X‐35, which induced the production of large amounts of phytoalexins, killed the outer epidermal cells and two to three layers of underlying sub‐epidermal cells. Cells adjacent to these dead cells were affected but not killed by this treatment.The main group of isoflavonoids formed were the 5‐hydroxyisoflavonoids (kievitone and licoisoflavone A). The 5‐deoxyisoflavonoids (phaseollin, phaseollidin and phaseollinisoflavan) were present only at low concentrations.When cotyledons treated with Triton X‐35 were incubated in distilled water the major induced isoflavonoids were kievitone, which was located mainly in the cotyledons, and a compound tentatively identified as 2′,4′,5,7,‐tetrahydroxyisoflavone, which was detected in the water medium.These results support the hypothesis that phytoalexin accumulation in the French bean is part of a wound response and involves an interaction between dead cells and their neighbouring live cells.