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

以13&gt；C和15&gt；N为示踪剂，定量研究了植物对碳、氮的获取、分配和利用动态。分配与利用系统：(1)缺氮降低了水稻光合作用碳向根部的分配。植株对氮素缺乏的反应既受植株发育阶段的影响，也受根节位置的影响。(2)在生殖生长期，缺氮增加了新吸收碳在根系呼吸中的贡献率。(3)从孕穗期到抽穗期，与下节根相比，氮素缺乏对上部节根呼吸利用微弱同化碳的影响较大。(4)遮荫2天后，水稻体内的分配格局发生了较大的变化。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并未减少。吸收系统：(1)紫花苜蓿幼苗吸收NH4-N的能力强于吸收硝态氮的能力，这与根系发育有关。(2)日本杉木纯林通过与Frankia共生固氮获得还原氮。氮素固定总量估计为57千克公顷-1年。

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>.