Quantitative simulation on dry matter partitioning dynamics of unit organs in above-ground rice

Chinese. 定量描述水稻植株地上部单位器官（叶片、叶鞘、节间、稻穗）干物质的动态分配过程，为作物形态建成模拟和可视化表达奠定基础。通过不同水稻品种和水氮试验中主茎和分蘖单位叶片、茎鞘及穗的干物质与水分及氮素含量的连续观测和定量分析，构建水稻地上部各单位器官干物质分配指数动态模型。模型采用线性和指数方程描述了叶片、茎鞘及穗单位器官分配指数随GDD的动态变化过程；分别用指数方程及一元二次方程描述了叶片、茎鞘及穗最大单位分配指数随不同叶位、鞘位以及穗位的动态变化过程；另外，以叶片、茎鞘及穗的氮素和水分因子法分别描述了水氮限制对各单位器官干物质分配过程的定量影响。利用独立的水稻田间试验资料对所建模型进行了初步的测试和检验，主茎与分蘖各单位器官干物重的观测值与模拟值的根均方差分别为0.93、0.81及6.8 kg•ha-1。本模型可较好地模拟不同生长条件下水稻不同茎蘖各单位器官干物质动态的变化过程。

English. Modeling dynamics of the dry matter partitioning among unit organs (leaf, sheath, internode and panicle) in rice is an important task for realizing virtual and digital plant growth. In the past years, some great progresses had been made on the dynamics of dry matter partitioning among leaves, stem and sheath, and panicles of rice, but the dry matter partitioning among unit organs of plant was seldom addressed. The present study was conducted to develop a simulation model on the dry matter partitioning dynamics for various unit organs of rice having relation to GDD. Four experiments were carried out involving different nitrogen rates and water regimes with four rice cultivars, and time-course observations were made on the dry matter changes in different unit organs on stem and tillers. The results showed that the dynamic change of the unit organ partitioning index could be characterized by linear and exponential equation, respectively for leaf, internode and sheath, and panicle in relation to accumulated GDD. The changes in the maximum partitioning index for unit organ could be described by exponential equation (unit leaf and sheath) and quadratic equation (unit panicle) with different leaf, internode and sheath and panicle positions on main stem and tillers. In addition, the effects of nitrogen and water conditions on the dry weight and partitioning index for unit organs were quantified through the effectiveness values of nitrogen concentration and water content in unit organs. The model was validated by the independent field experiment data involving different rice cultivars and nitrogen rates. The average RMSEs between the simulated and observed values for the dry weights of unit organs on main stem and tillers under varied nitrogen and water levels with different cultivars were 0.93, 0.81, and 6.8 kg•ha-1 for leaf, internode and sheath, and panicle, respectively. The results indicated that the present model had a good performance in predicting the dynamic changes in the dry weight and partitioning index for different unit organs in rice under different growth conditions, and thus it will be a foundation for further constructing digital and visual organ growth system in rice.