Reversal of the inhibition of photosynthesis by herbicides affecting hydroxyphenylpyruvate dioxygenase by plastoquinone and tocopheryl derivatives in Chlamydomonas reinhardtii.

Isoxaflutole or pyrazolate inhibition of tocopherol and plastoquinone biosynthesis in the green alga Chlamydomonas reinhardtii Dang leads to the inactivation of photosystem II and the degradation of its reaction centre D1 protein when exposed to strong light. Cell-permeable short-chain derivatives of plastoquinone and tocopherol were tested in the reversal. Addition of decyl-plastoquinone reverses herbicide-induced inhibition of photosynthesis and inactivation of photosystem II in short-time (1 h) exposure of the algae to high light. In high light longer than 1 h, decyl-plastoquinone alone loses effectiveness, but a synthetic permeable tocopheryl derivative retards the inhibitory effects on photosystem II and on the degradation of the D1 protein. This indicates that tocopherol deficiency induced by the herbicides makes a major contribution to their secondary mode of action in high light stress.