Effect of CO_2 enrichment on carbon metabolism of rice plants

在这项研究中，我研究了CO_2增加对水稻植株碳代谢的影响。首先，以自由空气CO_2增施工程水田上的水稻植株为材料，研究了增施CO_2对~(13)C光合作用产物分配和运转的影响。结果表明，在增施CO_2的条件下生长的植物的光合作用产物比在环境条件下生长的植株更有效地向果穗转移。此外，在增施CO_2的条件下，抽穗期叶鞘中储存的淀粉比环境条件下的植株更快地转移到果穗中。这些结果表明，CO_2浓度升高促进了碳向库器(耳朵)的转移和分配。其次，在不同CO2浓度下种植水稻植株，研究其对叶片光合作用的影响。光合作用和光呼吸所消耗的能量随着大气CO2浓度的增加而减少。因此，CO_2的富集会产生更多的过剩能量。然而，由于C02富集态植物的生长与常温条件下生长的植物一样好，多余的能量可能会被替代系统的激活所浪费。此外，CO_2的富集会使CO_2从大气到叶绿体羧化部位的通量变得更加困难。

In this study, I examined the effect of CO_2 enrichment on carbon metabolism of rice plants. Firstly, the rice plants grown on the paddy field of Free Air CO_2-enrichment Project were used to investigate the effect of CO_2-enrichment on the distribution and translocation of photosynthate using 13C. As a result, the photosynthate in the plants grown under CO_2-enrichment condition had more effectively shifted to the ear than those under ambient condition. Moreover, in the plants grown under CO_2-enrichment condition the starch stored in leaf sheath at heading stage was shifted into ears more rapidly than in those under ambient condition. These suggested that CO_2-enrichment would promote the translocation and distribution of carbon into sink organ (ears). Secondly, the rice plants were grown under various C0_2 concentrations to examine the effect on leaf photosynthesis. The energy used by photosynthesis and photorespiration decreased with the increasing in atmospheric CO_2 concentrations. Therefore, the C0_2 enrichment was thought to make the more excess energy. However, because the plants under C0_2 enrichment condition grew as well as those under ambient condition, the excess energy might be wasted by activation of alternative system. Moreover, the CO_2-enrichment made the flux of CO_2 from atmosphere to carboxylation site at chloroplast more difficult.