| The carbon dioxide concentration of the earth's atmosphere and frequency and intensity of rainfall are predicted to change in future years. The resulting changes could have considerable impact on crop production. The objective of this study was to evaluate responses of rice leaves to CO{dollar}sb2{dollar} concentration and water management for rice grown in controlled environmental chambers. Leaves of rice plants responded differently to CO{dollar}sb2{dollar} concentration and various water managements. High-CO{dollar}sb2{dollar} concentration significantly increased leaf photosynthetic rate during the study. On several dates, leaf soluble protein responded negatively by decreasing under increased CO{dollar}sb2{dollar} concentration. Nevertheless, leaf chlorophyll concentration of leaves of high-CO{dollar}sb2{dollar} treatments was significantly higher compared to that of low-CO{dollar}sb2{dollar} treatments. High-CO{dollar}sb2{dollar} treatments significantly increased leaf sucrose, starch and fructose concentration by 0.0 to 25.8%, 0 to 40.9% and 12.2 to 64.0%, respectively. High-CO{dollar}sb2{dollar} concentration had significant enhancing effects on sucrose and starch accumulation during early reproductive phases, but not during later reproductive phases. The difference in leaf starch, sucrose, and fructose concentration between leaves grown at elevated and current CO{dollar}sb2{dollar} diminished with plant maturity. High-CO{dollar}sb2{dollar} concentration also increased SPS activity throughout the season.; Water stress treatment significantly affected a number of variables during panicle initiation and anthesis stages. Water stress caused major reductions in leaf photosynthetic rate, leaf chlorophyll, and soluble protein, and water deficit periods also caused major decreases in leaf sucrose, starch and fructose concentration, and also in SPS activity. Water stress had more profound effects on leaves of plants grown in low-CO{dollar}sb2{dollar} concentration. High-CO{dollar}sb2{dollar} plants were able to maintain leaf photosynthesis longer into the water deficit period and had smaller reductions in chlorophyll and fructose concentration compared to ambient CO{dollar}sb2{dollar} plants. |
