Department of International Agricultural Development, Tokyo University of Agriculture, Tokyo 156-8502, Japan.
Physiol Plant. 2012 Apr;144(4):335-45. doi: 10.1111/j.1399-3054.2011.01563.x. Epub 2012 Feb 15.
Plants develop branches profusely when grown solitarily, while less so when grown in a dense stand. Such changes in architecture are associated with changes in dry mass allocation and nitrogen use. Here, we studied what traits in plant growth and nitrogen use were influenced by different light climates in the stand. Annual plants (Xanthium canadense) were grown solitarily or in a dense stand. Dry mass growth was analyzed as the product of the net assimilation rate (NAR) and leaf area (LA). Nitrogen use efficiency (NUE) was analyzed as the product of nitrogen productivity (NP) and the mean residence time (MRT) of nitrogen. These growth variables were further factorized into their components. Solitary plants maintained a high NAR, whereas plants in the dense stand decreased the NAR due to mutual shading. Plants in the dense stand developed a larger LA with a higher specific leaf area than solitary plants. Solitary plants had higher NUE due to higher NP. A temporal increase in NUE was attributed to the increase in MRT of nitrogen. Light climate was different between solitary and dense-stand plants, but they took up a comparable amount of nitrogen and used it differently in response to the given light climate. NUE was thus demonstrated to be a useful tool for analyzing the mechanism leading to different N use in plant growth.
植物在单独生长时会大量分枝，而在密集的群体中生长时则分枝较少。这种结构上的变化与干物质分配和氮利用的变化有关。在这里，我们研究了植物生长和氮利用的哪些特征受到群体中不同光照条件的影响。一年生植物（苍耳）单独生长或密集生长。干物质生长分析为净同化率（NAR）和叶面积（LA）的乘积。氮利用效率（NUE）分析为氮生产力（NP）和氮平均停留时间（MRT）的乘积。这些生长变量进一步分解为它们的组成部分。单独生长的植物保持较高的 NAR，而密集生长的植物由于相互遮荫而降低了 NAR。与单独生长的植物相比，密集生长的植物具有更大的 LA 和更高的比叶面积。由于 NP 较高，单独生长的植物具有较高的 NUE。NUE 的时间增加归因于氮 MRT 的增加。单独生长的植物和密集生长的植物的光照条件不同，但它们在不同的光照条件下吸收了相当数量的氮，并以不同的方式利用氮。因此，NUE 被证明是分析导致植物生长中不同氮利用机制的有用工具。
