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Published online by Cambridge University Press: 05 December 2011
A study has been made of the effects of natural antioxidants (cysteine and ascorbate), commonly used in media for isolation of organelles and in reaction mixtures, on light-induced proton uptake and photophosphorylation in chloroplasts of pea and maize. These plants were chosen because of their different levels of resistance to unfavourable environmental conditions. Conditions for studying chloroplasts in different functional states were modelled and it was shown that the antioxidants exerted a regulatory effect on light-induced proton uptake and ATP formation. The direction of the response was dependent on the initial state of the chloroplasts and was correlated with the concentrations of free and total sulfhydryl groups. A scheme for regulation of energy transformation in chloroplasts, including antioxidants and free radical oxidation, is proposed.