色赤杨光合作用与根瘤氮代谢的关系

Relationship between photosynthesis and nitrogen metabolism in the nodules of Alnus tinctoria Sarg

在放线菌结瘤植物(Actinorhizal plants)与放线菌Frankia的共生体系中,固氮酶(N_2ase)活性与所提供的光合产物的量密切相关。通过在同一天的不同对间内,对同株色赤杨光合作用和根瘤中的N_2ase比活、NH_4^+含量、还原糖含量以及总氮量的变化所做的同步测定结果表明,N_2ase比活的最高峰迟后于光合强度的最高峰;在根瘤内部,NH_4^+含量和还原糖含量都与N_2ase比活呈负相关,而总氮量则与N_2ase比活呈正相关。本文对这一现象进行了讨论,并且推测还原糖作为光合作用产物的衍生物,直接影响根瘤的固氮作用,它不仅为N.2ase提供固氮所需的能量,而且为固氮产物NH_4^+提供受体。

In the symbiotic system of actinorhizal plants and Frankia, nitrogenase activity is closely relied on the photosynthetic products of plants. To approach this physiological relativity, we have synchronously examined the photosynthetic rate, N_2ase activity, NH_4^+, reducing sugar and total nitrogen contents in the nodules of the same plant of Alnus tinctoria Sarg at different time during the day. The results indicated that the maximum of N_2ase acti vity appeared behind the maximum of photosynthetic rate. This suggested that it was photosynthetic products that influenced the N_2ase activity, and the transport of the pro ducts from leaves to nodules took a certain time. In the nodules, when NH_4 + and redu cing sugar contents decreased, the N_2ase activity increased and at the meanwhile,the to tal nitrogen content increased too. These phenomena had been discussed. It can be con cluded that reducing sugar as the derivatives of photosynthetic products influences immediately on nitrogen fixation and can provides not only the energy for nitrogen fixa tion, but also the carriers for NH_4^+ which was the first product of nitrogen fixation.