Paraquat tolerance in a photomixotrophic culture of Chenopodium rubrum.

A paraquat tolerant line of Chenopodium rubrum has been compared with paraquat susceptible cultures, in terms of growth, chlorophyll content, photosystem I partial reactions, and the activities of some enzymes involved in detoxification of harmful oxygen radicals. Results indicate that paraquat tolerance is manifested through increased activity of superoxide dismutase, peroxidase and catalase, in the tolerant line, only in the presence of paraquat. The behaviour of the paraquat tolerant. and susceptible cultures in the absence of paraquat is quite similar.