[ESR study of electron transport in photosynthetic systems. VII. Effects of temperature on the processes of electron transport between two photosystems and the structural state of the chloroplast membrane]

Abstract

Redox transients of P700 in bean chloroplasts induced by far-red continuous light and brief flashes (t1/2 = 7 musec) of white light were studied under various temperatures. It has been shown that light-induced electron transport between two photosystems occurs at temperatures from -5 degrees to 45 degrees. At temperature interval 5 divided by 30 degrees photosystem 2 donates electrons to P700+ in response to the flash with the maximum efficiency. The number of electrons donated from photosystem 2 does not depend on the temperature in the range 5 divided by 30 degrees. The rate of electron transport between photosystems increases when the temperature is increased from -5 degrees to 20 degrees and does not depend on the temperature above 20 degrees. Structural states of the lipid region of the thylakoid membrane were studied by the spin label method. It was shown that the flexibility and the rate of molecular motion of different spin-labeled fatty acids were increased after temperature variations from -10 degrees to 50 degrees. A correlation between the structural state of the lipid region of thylakoid membrane and the rate of electron transport was found.