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

以^ C和^ N为示踪剂，定量研究了植物对碳、氮的吸收、分配和利用动态<13><15>.分配与利用系统：（1）缺氮降低了水稻光合碳向根系的分配。植株对氮素胁迫的反应受生育期和根系节位的影响。(2)在生殖生长阶段，氮素缺乏增加了根系呼吸中新同化碳的贡献率。(3)孕穗至抽穗期，氮素缺乏对上部根系呼吸利用新同化碳的影响大于下部根系。(4)2天的遮荫大大改变了水稻植株的分配格局。在根系中，遮荫抑制了新根的发育，但对根系的同化物供应量没有减少.采集系统：（1）苜蓿幼苗对铵态氮的吸收明显高于硝态氮，这与根系的发育形态有关。(2)日本赤杨纯林通过与Frankia共生固氮获得还原氮。据估计，每年固定的氮量为57公斤/<-1>公顷<-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>.