不同光环境下桂花幼苗的构型差异

通过对不同光照条件下桂花幼苗的冠形、分枝率、叶片在树冠中的空间分布等特征进行研究,结果表明桂花幼苗构型发生了明显的可塑性适应:其树冠对光照条件的变化有显著的可塑性响应。在林隙中的幼苗受光的间歇性影响,总体分枝率明显小于全光、林冠下的幼苗分枝率。全光的幼苗叶片集中于二级枝,叶片长度和叶片面积相对较小,对光照利用充分;而林隙中的幼苗叶片集中于一级枝,避免处于植冠内侧受到遮蔽,表现出较大的叶片长度和叶面积;林冠下的叶片较均匀分布在一、二级枝上,叶片总数量较少,枝条高生长较全光下明显。幼苗在总体分枝格局中表现出独自的特点,即强光环境下产生短枝和高分枝率,在适度庇荫条件下产生长枝及低分枝率,在强度庇荫条件下以较长枝和较高分枝率来同时满足高生长和横向生长的需求。

The Architectural Variation of Osmanthus fragrans Seedlings in Different Light Conditions

In this paper,crown shape,bifurcation ratios and leaves of Osmanthus fragrans seedlings were examined.The results showed that the architecture of seedlings was modified plastically in response to different light conditions.Because the seedlings that live in gaps get light intermittent,overall bifurcation ratio are significantly lower than that under canopy and full sun.Under full sun,the seedlings had their leaves distributed at the second-order branch with comparatively small length and area which can help seedlings use light fully.While,in gaps,seedlings seemed to have their leaves distributed at the first-order branch with comparatively large length and area to avoid being shaded by canopy.Under canopy,the leaves with small sum are distributed relative uniformly from the first-order branch to the third-order branch,and the height growth of branch is significantly higher than that under full sun.In conclusion,branching patterns of O.fragrans seedlings have unique traits: under strong radiation,O.fragrans seedlings can give rise to short branch and high bifurcation ratio.Under adequate shade condition they can give rise to long branch and low bifurcation ratio.Under intense shade condition they can give rise to comparatively long branch and comparatively high bifurcation ratio for height and horizon growth.