Abstract: Simulating bending branches is an important part of plant simulation and L-system is one of the significant methods of it.But it requires plenty of productions if L-system is applied to simulate bending branches.In this paper，functional L-system is presented，through adding the bending symbols and curvature functions to the productions.When modeling shapes of plants using functional L-system，without changing the number of productions，various shapes of trees with the same topological structure will be produced through adjusting the curvature functions.Functional L-system is a very concise description in modeling bending branches of plants，and the length of the branches can be easily controlled in programming.

Key words: simulation of shapes of plants, L-systems, curvature functions, bending branches

摘要： 弯曲枝条的模拟是植物模拟的重要组成部分，L-系统是植物模拟的重要方法之一。如果用L-系统模拟弯曲的枝条，则需要大量的产生式。通过在产生式中增加弯曲符号以及描述弯曲程度的曲率函数得到了函数L-系统。利用函数L-系统模拟植物，在不改变产生式个数的情况下，通过调整曲率函数能够绘制出相同拓扑结构，但整体形态差异较大的植物；利用函数L-系统模拟具有弯曲枝条的植物，产生式简洁，同时在编程时，容易控制枝条的长度。

关键词: 植物形态结构模拟, L-系统, 曲率函数, 弯曲枝条