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We developed transgenic rice plants (Oryza sativa L. cv. Daeribbyeo) overproducing cytosolic glutathione reductase (GR) using a GR gene from Brassica campestris and studied their response to photo-oxidative stress in the presence of methyl viologen (MV, 10 and 50 µM concentrations) under room (25 °C) and moderately elevated (35 °C) temperature by analysis of chlorophyll (Chl) a fluorescence parameters (F V /F M , q N , and q P ) and of Chl content. Elevated temperature enhanced and accelerated the photo-oxidative damage to photosynthetic apparatus expressed mainly by a fast decrease of q N . Higher temperature supported the protective reaction in transformed rice plants for lower MV concentration (10 µM) and eliminated the enhanced tolerance of photosystem 2 photochemistry to photooxidative stress for higher (50 µM) MV concentration. Different mechanisms and temperature dependence of oxidative and protective reactions explain the results.

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