Amendment of environment by plant : Response of plant to elevated CO_2 Concentration

为了利用植物保护和改善环境，从光合作用产物和氮素同化物的运转方面研究了大豆对CO2浓度升高的响应。大豆(Glyine max cv.)在温室条件下，在籽粒灌浆期暴露于CO_2浓度(35和100PaCO_2)中17-21天。试验一，CO_2浓度和硝酸盐水平对硝酸盐还原的影响，氮素同化物的分配：(1)在有硝酸盐存在的情况下，增施CO_2显著增加了整个植株的还原氮量，但在不施硝酸盐的情况下没有观察到这种影响。(2)高浓度CO_2处理后，叶片硝酸还原酶活性升高。(3)增加CO_2浓度可使上部叶顶生小叶输出更多的氮素。实验二，CO_2浓度和去荚对植物生长的影响：(1)CO_2浓度升高促进了植物的生长。(2)随着CO_2浓度的升高，~(13)C和~(15)N的输出量均减少，且以~(15)N的减少更为明显。(3)去除角果后，叶片、叶柄和茎中各种氨基酸的N原子过剩百分数和浓度不受CO_2浓度的影响，而天冬酰胺和脯氨酸的这些值随着脱荚处理的增加而增加。这表明，当库活动受限时，一些氮源化合物在叶柄和茎中被同化。目前的研究表明，CO2浓度升高不仅影响植物体内的碳代谢，而且还影响植物的氮代谢。

For protection and amendment of environment by plant, the response of soybean to elevated CO_2 concentration was examined in terms of translocation of photosynthate and nitrogenous assimilates. Soybean (Glycine max cv. Tamahomare or Greenhormer) was exposed to CO_2 concentration (35 and 100 Pa CO_2) for 17-21 days at the grain filling stages under controlled glasshouse conditions. In the experiment 1, nitrate concentration in the culture media was changed, and in the experiment 2, pod removal treatment was also applied.Experiment 1, Effect of CO_2 concentration and nitrate levels on nitrate reduction, distribution of nitrogenous assimilate : (1) While CO_2 enrichment significantly increased reduced-N amount in the whole plant under the presence of nitrate in the culture media, such effect was not observed without application of nitrate. (2) Nitrate reductase activity in leaves increased after imposed to elevated CO_2 concentration. (3) More ^<15>N fed from a terminal leaflet of an upper leaf was exported by CO_2 enrichment. Experiment 2, Effect of CO_2 concentration and pod removal on partitioning of ^<13>C and ^<15>N : (1) The elevated CO_2 concentration led to enhancement of plant growth. (2) The elevated CO_2 concentration decreased export of both ^<13>C and ^<15>N, and the decrease was more pronounced in the latter. (3) While ^<15>N atom % excess and concentration in various amino acids in leaf petioles and stem was not affected by CO_2 enrichment, these values in asparagine as well as proline were increased by pod removal. This suggests that some nitogenous compounds are assimilated in petioles and stem when sink activity is limited. The current study suggest that CO_2 enrichment affects not only carbon metabolism but also nitrogen metabolism in plant.