L-system based dynamic root growth model formulation of aquatic plants

Abstract

植物根系在地球生物圈物质循环中起到关键性作用.陆生植物中目前基于根系具有对称性和自相似性假设建立的L系统已经做了较好研究，但在水生植物中相关的研究较少，更缺乏根系动态生长模型的构建.本文拟通过发展L系统来模拟水生植物从初生结构到次生结构，从简单根系到复合根系的动态生长过程.根系动态生长模型主要包含根系伸长规则和根系分支规则，并包含由主根与侧根的夹角θ和径向角γ确定初始根系生长方向.特别地，系统建立了2种代表性水生植物——世界上入侵严重的水生植物凤眼莲（Eichhornia crassipes）和被研究较多的水生植物穗状狐尾藻（Myriophyllum spicatum）根系动态生长模型.结果表明凤眼莲成熟根系总长度可达到2042.78 m，可能有利于其占据较多的空间和资源，使得凤眼莲在与本地植物的竞争中占有优势.穗状狐尾藻的总根系长度为73.08 m，由于穗状狐尾藻表现出最为典型的叉状分支构型，表明其对沉水生长环境有较好的适应性.;Root systems play a vital role in material circulation in the biosphere. Based on the two hypotheses of symmetry and self-similarity in the root system, the L-system of terrestrial plants has been well established. However, related research in aquatic plants, particularly for the dynamic root growth model, is rare. This study simulated the dynamic growth processes of a primary to secondary root structure from simple roots to complex roots of aquatic plants. The dynamic root growth model mainly includes root elongation and branching rules and determines the initial root growth direction of the intersectional angle θ and radial angle γ between the main and lateral roots. Specifically, the dynamic root growth model formulations of two representative aquatic plants, the cosmopolitan invasive aquatic plant, water hyacinth (Eichhornia crassipes), and the relatively most studied aquatic plant, Eurasian watermilfoil (Myriophyllum spicatum), were established by applying the L-system. The total length of the root system of mature E. crassipes can reach 2042.78 m, indicating that the species has a high nutrient absorption capability. This may favor resource exploitation, facilitating its competitive ability with native plants. The total length of the M. spicatum root system is 73.08 m; owing to its typical dichotomous branching, this plant has a relatively high adaptation to the aquatic environment.