Simulating three-dimensional structure, growth and development of rice plants

水稻产量受形态性状的影响，这些性状在很大程度上取决于环境和基因型。本研究旨在建立一个模型，模拟受气候因素和耕作方式影响的水稻植株结构、发育和生长。整体模型尚未完成，但我们建立了物候、叶片外观、分蘖、茎伸长、器官空间分布和冠层光环境的子模型。利用富山地区近15年的田间观测资料，对基于发育阶段和温度的叶片外观模型进行了验证，较好地解释了叶片数的年际变化。利用节点位置的分蘖出苗概率来模拟温度和株距的影响。根据在京都和札幌获得的Koshihikari的形态资料，我们观察到，在穗形成前出现的叶片，层长在地点、年份和氮水平之间的变化较小，在穗形成后逐渐变大。CO_2升高对不同基因型的影响不同。叶片尺寸的基因型差异主要表现在长宽比上，而叶片面积可以用长度、宽度和一个常数（0.75）的乘积来估计。12个三角形可以很好地模拟叶片的三维形状，并用于模拟水稻冠层的光环境。将叶片N和CO_2的影响纳入光合作用模型。这些发现为我们提供了一个评估冠层光合作用取决于冠层结构和环境的工具。

Rice productivity is influenced by morphological traits that depend largely on environments and genotypes. The present study aimed to develop a model that simulates rice plant structure, development and growth as affected by climatic factors and cultivation practices. The overall model has not been completed but we developed the submodels of phenology, leaf appearance, tillering, stem elongation, spatial distribution of organs, and light environments in the canopy. The leaf appearance model based on developmental stage and temperature was tested with the field observations in Toyama for the past 15 years and explained well the yearly variation in leaf number. Probability of tiller emergence by node position was developed to simulate the effects of temperature and plant spacing. Based on the morphological data of Koshihikari obtained in Kyoto and Sapporo, we observed that variation in lamina length between locations, years and N levels was small in leaves that appeared before panicle initiation and became progressively larger thereafter. The effect of elevated CO_2 was different among genotypes. Genotypic variation in lamina dimension was marked in length : breadth ratio, but the lamina area could be estimated by a product of length, breadth and a constant (0.75) for various genotypes. Three-dimensional shapes of lamina could well be approximated by 12 triangles, which were used to simulate light environments in the rice canopy. The effects of leaf N and CO_2 were incorporated into the photosynthesis model. These findings provide us with a tool to assess canopy photosynthesis depending on the structure and environments of the canopy.