生长期-定时一年生植物群体光合产物的最优分配策略的理论分析

本工作建立了一个一年生植物群体的生长模型,利用以梯度法为基础的离散系统最优控制的计算方法,计算并分析了一年生植物群体光合产物的营养器官间分配的最优策略,以及这一策略对植物群体最大生长速率和消光系数的依赖关系。用Pontryagin最小值原理和奇异最优控制的条件证明了光合产物的最优分配方法是:在营养和生殖生长并行阶段,群体叶片的死亡量恰好等于新形成量,植物干重随时间线性增加。

OPTIMAL ALLOCATION OF PHOTOSYNTHATES BETWEEN VEGETATIVE AND REPRODUCTIVE PARTS OF ANNUAL PLANTS WITH CONSTANT GROWTH PERIOD

A model for annual plant growth which takes account of mutual shading of leaves has been developed. By using the gradient method, optimal allocation pattern of photosynthates between vegetative and reproductive parts has been calculated. The optimal pattern is to allocate at first all photos. nthates to vegetative parls( 1st period), and then to both vegetative and reproductive parts (2nd period), and at last all to reproductive parts (3rd period). This pattern differs from those published before in which an transitional phasc(2nd period) was proposed for a simultaneous growth of vegetative and reproductive parts. Calculation using exemplary data for th is model shows that (1) the intermediate period (transitional stage) is longer for plants with horizontal leaves and shoiter for those with erect leaves; (2) in a relatively large range of maximal canopy growth rates and extinction coefficients, the length of the 1st period changes only slightly.By using Pontryagin's minimum principle,and based on the necessary conditions for optimal singular control, it has been shown that in the transitional phase the amount of leaves lying at the bottom of the canopy equals that being newly formed on the top, and thus leaf area index is kept constant and the weight of plants increases linearly with time.