Basmati rice (Oryza sativa L.) cultivars viz. PRH-10 (pusa rice hybrid-10) and PS-2 (Pusa Sugandh-2) were grown under two different day/night temperatures (31/24°C, 35/28°C) at ambient (370 µmol/mol) and elevated (550 µmol/ mol) carbon dioxide (CO 2 ) concentration, respectively, to characterize how an increase in CO 2 and temperature affects rice photosynthesis and carbohydrate metabolism. At elevated CO 2 , the photosynthetic rates increased under both the temperature regimes, compared with plants grown at ambient CO 2 . The photosynthetic rate, sucrose-P synthase (SPS) activity and accumulation of soluble sugars and starch were higher in PRH-10 (pusa rice hybrid-10), compared to PS-2 (Pusa Sugandh-2). Elevated temperature decreased the photosynthetic rates both under ambient and elevated CO 2 conditions. The SPS (sucrose-P synthase) activity and the accumulation of soluble sugars and starch were enhanced at elevated CO 2 under both temperature regimes compared with plants grown at ambient CO 2 . The up-regulation of SPS (sucrose-P synthase) under elevated CO 2 and temperature would be beneficial for growth and productivity of rice plants for the future climatic conditions.

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The aim of our work is to study gas exchange and antioxidant system in nine wild solanaceous species Solanum indicum, Solanum macrocarpon, Solanum acculeatissimum, Solanum sysimbrifolium, Solanum nigrum, Solanum viarum, Solanum insimum Solanum torvum, and Solanum macranthum under water logging condition. Experiments were laid in factorial completely randomized design with three replications. Photosynthesis and stomatal conductance decreased and closure of stomata was quick during flooding conditions in all the Solanum species. Species Solanum torvum performed photosynthetically better under flooding and also had better stomatal conductance. The antioxidants like SOD, catalase and peroxidase activity was significantly increased during the period of waterlogging and lipid peroxidation (MDA) content was decreased in tolerant Solanum species. An increase in the some parameters associated with oxidative stress, namely peroxides production, lipid peroxidation, and electrolyte leakage, reveals that root oxygen deficiency caused photooxidative damage in all rootstocks of solanaceous species. The ability to maintain a balance between the formation and detoxification of activated oxygen species appeared likely to increase the survival potential and the tolerance of the plants against varying oxidative stress. On basis of our observation, we conclude that species with higher photosynthetic rate and antioxidant system had improved waterlogging stress tolerance.