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

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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.