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)通过对4个玉米根系样本的观测，提取了描述根系整体特征的元规则，如根系分布的幂尺度、根密度方程和根系轮廓曲线方程。2)基于随机L系统定义了节状和一阶分枝的分枝群规则。3)参考文献假设根尖章动和几何作用力曲率为根尖运动规则。4)将上述三种规则集成为松散控制的小尺度规则，并通过改变固体密度来引入“环境开关”，从而产生了“分级根生长模型”。5)不同土壤密度条件下的根箱试验证明，土壤密度的变化对玉米根系的形成有很强的影响，该模型也能很好地模拟这些特性。6)本工作建立的二维根系生长模型，虽然尚未建立三维根系生长模型，但对控制二维土壤密度条件下的根系生长有较好的预测效果。

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.