高CO_2浓度对大豆不同叶位叶片叶绿体淀粉粒积累的效应

EFFECT OF ELEVATED CO_2 CONCENTRATION ON THE STARCH GRAIN ACCUMULATION IN CHLOROPLASTS FROM SOYBEAN LEAVES AT DIFFERENT NODES

对高CO_2浓度下生长的大豆(Glycine max(L.)Merr.)不同叶位的叶片进行了电镜观察,揭示出大豆不同叶位叶片的叶绿体对倍增的CO_2浓度反应不一。其显著的超微结构差异特征是:1.叶位居中的叶片叶绿体积累的淀粉粒不仅很大,而且最多,有的叶绿体中的淀粉粒可达20个,几乎充满着叶绿体的基质空间。2.下位叶叶绿体的淀粉粒积累较多,通常为2～5个;3.上位叶叶绿体所含淀粉粒既小又少,虽然有的叶绿体中也积累有3～4个淀粉粒,但大多数叶绿体中所含淀粉粒仅有1～2个。以上结果联系到大豆中位叶的光合作用速率较高及对籽粒产量起作用最大来讨论是很有意义的。

Soybean ( Glycine max (L.) Merr.) plants were grown under ambient and elevated CO2 (plus 350 L/L) concentration in cylindrical open-top chamber to examine their effects on the ultra-structure of chloroplasts. The upper,lower and mid-node leaves were harvested after 7 days' full expansion under different CO2 concentrations and ultrathin section were prepared for transmission electron microscopy. In general, the average content of starch grains and thylakoid membranes in the chloroplasts under the elevated CO2 concentration were always higher than the control. Under higher CO2 concentration, there were smaller and less starch grains in the chloroplasts from upper-node leaves than those from mid-node leaves. The shape of their starch grains changed from elliptical to oval, and their thylakoid membranes and grana remained normal. At lower-node leaves, one or two oval, or three flater starch grains accumulated in the chloroplasts. In the mid-node leaves,however, some chloroplasts under higher CO2 concentration had rather large flat elliptical starch grains which could consequently cause disruption of grana and stroama thylakoids in the chloroplasts, whereas in other chloroplasts, the thylakoid membranes and grana were not deformed as the starch grains were smaller and elliptical. On the other hand, under higher CO2 concentration, the stacking degree of thylakoid membranes and starch grains accumulation in the mid-node leaves were significantly higher than those in the lower-node leaves, and slightly higher than the upper-node leaves. These results, in agreement with the chlorophyll contents and photosynthetic rate which reported by other authors in the past, indicated that the ultrastructure response of the chloroplasts from different leaf nodes of soybeen under elevated CO2 concentration were different. The seed yield of soybean at different nodes was decreased gradually from mid-nodes towards both upper- and lower-nodes. The greatest effect of elevated CO2 concentration on seed yeild was at the mid-node leaves. The variation of seed yields of soybean at different nodes under elevated CO2 concentration was in concert with the change in the ultrastructure of chloroplasts and in turn the change in their photosynthetic rates of leaves at different nodes.