ROOT GROWTH SIMULATION USING L-SYSTEMS

Dynamic root growth simulation is an important tool when analysing the mecha- nisms within the rhizosphere. The concentration of nutrients in the soil as well as water content is strongly dependent on the root structure. On the other hand root growth is effected by the nutrient concentration and water supply as well as other soil parameters. As a result realistic root growth models are often coupled with models describing the plant-soil interactions. In this paper we present an L-System algorithm which makes it possible to easily create 3-dimensional geometries of growing plant root systems. Furthermore we discuss possibilities of coupling these root growth system models with arbitrary models describing plant-soil interaction. The model is implemented in Matlab, which makes it easy to couple it to existing Matlab or Comsol models. 1. Introduction. In modelling and simulation of plant-soil interactions accurate root growth models are of major importance. In many cases those models are coarse approximations of growing root systems. Many models directly compute root length densities without including root architecture or branching structure. These densities then provide the basis of source and sink terms to nutrient uptake or exudation models ((1), (2)). Considering discrete 3-dimensional time dependent root growth models has cer- tain advantages. Firstly, it makes it easier to describe the developmental process such as root branching, root diameter or root growth angles. Secondly, it enables us to link the discrete model to a model which describes plant-soil interactions. This coupling makes it possible to describe changes of plant morphology due to water content or distributions of nutrients in the soil. Finally, such models can be used to analyse the effects of root growth on plant nutrient uptake from soil. This is done by comparing the total nutrient uptake to coarser models obtained by averaging or homogenisation. There exist some powerful discrete root growth models ((3), (4), (5), (6)). However it is hard to completely understand their behaviour and couple them to arbitrary uptake and exudation models. Our aim is therefore to develop tools that can easily set up root growth models and link them to arbitrary uptake or exudation models implemented in Matlab or Comsol. It is important that global root system parameters from literature or experiments can be included in the model. As a result the code is kept simple by using the notation of parametrized L-Systems, and therefore it can be easily adapted to several applications.