Photosynthetic electron transport in thylakoids from cotton cultivars (Gossypium sp.) differing in tolerance to prometryn.

A method to determine photosynthetic electron transport in thylakoid membranes is described for Gossypium barbadense (cv. Pima S-7) and G. hirsutum (cv. DP 5415). These cultivars differed markedly in tolerance to prometryn, a PS II inhibitor. The rates of photosynthetic electron transport obtained were 245 μmole oxygen mg(-1) chl h(1). Plant age and leaf size influenced the activity of the thylakoid preparations. Thylakoids from leaves of plants 24 to 37 d and 50-70 mm in diameter had the highest activities; thylakoids from cotyledons, fully expanded leaves and young leaves had low activity. Thylakoids from both species had similar photosynthetic activities and I50's for prometryn, atrazine and diuron. Thus, tolerance to prometryn was not due to differential binding at D1 protein.