BRANCHING GROWTH MODEL OF ROOTS DEVELOPED UNDER VARIOUS SOIL BULK DENSITY CONDITIONS BASED ON EXTENDED L-SYSTEM

在薄根箱中模拟了不同土壤容重条件下玉米根系的分枝生长规律。1）描述根系整体特征的元规则，如根系分布的幂指数、根系密度方程和根系轮廓曲线方程，2）根据随机L-1方程定义了节根和一级分枝根的分枝生长规律，并对节根和一级分枝根的分枝生长规律进行了分析，得出了一级分枝根的分枝生长规律为：（1）节根和一级分枝根的分枝生长规律为：节根和一级分枝根的分枝生长规律4）将上述3种规则整合为松散支配小尺度规则的大尺度规则，并通过改变土壤密度引入“环境开关”，得到“层次根系生长模型”。5）不同土壤密度条件下的根箱试验表明，土壤密度的变化对玉米根系的形成有很大的影响，模型也能很好地模拟这些特性。6）本文建立的二维根系生长模型能很好地预测二维土壤密度条件下玉米根系的生长。虽然目前还没有建立三维根系生长模型。

Modeling the branching growth patterns of the maize root system developed under various soil bulk density in thin root boxes was carried out. The outputs of the work are as follows.1) Meta-rules which described an entire feature of root system, such as a power-scaling on the distribution of roots, a root density equation and an outline curve equation of root system, were extracted from the observation on four samples of corn root system obtained.2) Branching grouwth rules for nodal and first order branching roots were defined on the basis of stochastic L-systems.3)Nutation and georeacting curvature of root tip were assumed as root tip movement rules by references.4)Integrating three kinds of rules described above as large scale rules loosely governed small scale rules, and introducing an "environmental switch" by varying soid density yielded "Hierarchical Root Growth Model". Computer simulations by using the model depicted well the observed root systems.5)Root box experiments under various sois density conditions proved that the soil density variation strongly influenced the formation of the maize root system and these properties were also simulated well by the model.6)2D root growth model established in this work has given a good prediction of root growth under controlled 2D soil density conditions, though 3D root growth model has not established yet.