Dynamics of Partitioning of Carbon and Nitrogen in Plants : Responses to Environments and Growth Strategies

以^<13>C和^<15>N为示踪剂，定量研究了植物体内碳氮的获取、分配和利用动态。分配与利用体系：(1)氮素缺乏降低了水稻植株光合碳向根系的分配。氮素缺乏的响应受生育期和根系节位的影响。(2)在繁殖阶段，缺氮增加了根系呼吸中新同化碳的贡献率。(3)从孕穗期到抽穗期，与下节根相比，上节根对新同化碳的利用受缺氮影响较大。(4)遮荫对水稻植株的分配格局有较大影响。在根系中，遮荫抑制了新根的发育，但对根系的同化物供给量没有减少。获取机制：(1)苜蓿幼苗对铵态氮的吸收强于对硝态氮的吸收，这与根系发育有关。(2)日本产桤木纯林分通过与Frankia共生固氮获得降氮。固氮量估计为57 kg ha^<-1>年^<-1>。

Dynamics of acquisition, partitioning and utilization of carbon and nitrogen in plants were investigated quantitatively using ^<13>C and ^<15>N as a tracer.1. Partitioning and utilization system : (1) Partitioning of photo-assimilated carbon to the roots in the rice plant decreased by nitrogen deficiency. The response of nitrogen deficiency was affected by plant stage as well as nodal position of roots. (2) During the reproductive phase, nitrogen deficiency increased the percent contribution of newly assimilated carbon in root respiration. (3) From booting to heading, the utilization of mewly assimilated carbon by respiration in the upper nodal roots was largely affected by nitrogen deficiency, as compared with the lower nodal roots. (4) Partitioning pattern in the rice plant was largely changed by 2-days shading. In the root system development of new roots was depressed by shading but amount of assimilate supply to the roots was not decreased.2. Acquisition system : (1) Alfalfa seedlings preferred to absorb ammonium-N than nitrate-N,and this was associate with the development from of root system. (2) Pure stand of Alnus Sieboldiana grown in Japan acquires reduce nitrogen by symbiotic nitrogen fixation with Frankia. The amount of nitrogen fixed was estimated to be 57 kg ha^<-1> year^<-1>.