TETCYCLACIS AND ABSCISIC ACID-SENSITIVE REDUCTION OF EXTRACELLULAR FERRICYANIDE BY MESOPHYLL-CELLS OF VALERIANELLA-LOCUSTA AND LEMNA-GIBBA

Electron transport across the plasma membrane of Valerianella locusta mesophyll cells an intact fronds of Lemna gibba, induced by 10(-3) M ferricyanide, was inhibited by tetcyclacis, an inhibitor regarded to be specific for cytochrome P-450 mono-oxygenases. The effect was dependent on the concentration of tetcyclacis and the duration of preincubation. The apparent rate of transmembrane electron transport increased in the presence of catalase, indicating tetcyclacis-induced H2O2-production or additional tetcyclacis-independent H2O2 release. The findings suggest an interaction of cytochrome P-450 with the plasma membrane-located electron transport chain. This redox-chain could be involved in the degradation of abscisic acid, being located at the plasma membrane. This assumption is supported by the finding that ABA inhibits extracellular ferricyanide reduction.