植物生长过程中碳同位素分馏对气候的响应

HOW DOES THE CARBON ISOTOPE COMPOSITION RESPONSE TO THE CLIMATE DURING THE PLANT GROWING

探讨 C4 植物的碳同位素组成对气候的响应是碳同位素示踪研究的重要任务。观察了典型的 C4 植物玉米生长过程的碳同位素效应 ,结果表明 ,玉米在其生长季节里碳同位素组成有明显的变化。不同部位的叶片碳同位素组成变化不一样 ,顶部叶片变化较大 ,下部叶片变化则相对较小。这种变化受温度、水分和光照强度等多种气候要素的影响。同一株玉米 ,其顶部的叶片 δ1 3C值比下部叶片要偏正 ,而且随着玉米的不断生长 ,这一现象更加明显 。

The use of stable carbon isotope as climate proxies is widely accepted for climate reconstruction, but how the stable carbon isotope composition of C 4 plants responds to the climate is still unclear in the trace studies of the carbon isotope. In this research, we observe the carbon isotope discrimination of the typical C 4 plant, corn, during the growing period, and we find the obvious variation of the carbon isotope composition. The carbon isotope compositions of the top leaves vary more apparently than those of the lower leaves. This variation is related to several climate factors, such as temperature, moisture, the intensity of sunlight and the CO 2 level. Furthermore, to the same corn, the δ 13 C values of the top leaves are positive to those of the lower leaves, and this phenomenon is more obvious with the growing of the corn. We attribute it to the variation of the temperature and the intensity of the sunlight. The isotope fractionation during the growing process of corn indicates that the δ 13 C value increases when the climate is warm and dry. This will offer us the evidence for reconstructing the paleoclimate by using the carbon isotope of plants.