喜树幼苗的叶悬挂角和叶柄角对不同光环境的响应和适应

Acclimatization of Midrib Angle and Petiole Angle of Camptotheca acuminate Decne to Different Light Regimes in Evergreen Broadleaves Forests

对比研究了旷地、林窗及林下3种光环境下喜树幼苗叶悬挂角和叶柄角的光响应与适应性,结果表明:(1)在旷地、林窗和林下,光、热等生态因子的差异显著;(2)对于不同的光环境,喜树幼苗的叶悬挂角和叶柄角在旷地的变化幅度最大,林窗下次之,林下最小;(3)夏季晴天,在旷地、林窗和林下,喜树幼苗的叶悬挂角与叶柄角分别在16:00、14:00和12:00左右达到“峰”值,叶悬挂角分别约为140°、128°和112°,叶柄角分别约为67°、59°和55°;同时,在3种光环境下,夏季晴天喜树幼苗的叶悬挂角与叶柄角的日变化还表现出一定的协同互作关系,以叶悬挂角和叶柄角同时增大或减小来避开或捕获光辐射,这样即保证了喜树叶片有效避开强光,也确保喜树叶片对适度光辐射的最大利用。以上都是喜树叶片对光的捕获或避开所产生的一种适应效应。

As a special deciduous broadleaf tree in evergreen broadleaves forests, Camptotheca acuminate is a class Ⅱprotected plant in China. In this paper, the light response and acclimation of leaf inclination in three different light regimes （open, gap and understory） was compared. The results indicated that significant difference among different regimes existed in ecological factors such as PAR, temperature, Vpd and etc. In different light regimes, the extents of diurnal change of midrib angle and petiole angle of Camptotheca acuminate were different, and the highest extent existed in open, the second was in forest gap, and the least was in understory. The midrib angle and the petiole angle appeared at ＂peak＂ at 16：00, 14：00 and 12：00 respectively in these three light regimes in the sunny day in summer,correspondingly, the values of midrib angle were about 140°, 128° and 112°, and the values of petiole angle were about 67°, 59° and 55° respectively. In the sunny day, diurnal courses of midrib angle and petiole,angle of Camptotheca acuminate showed a certain cooperative relationship to some extents in strong light regimes. In order to effectively avoid strong light or assimilate moderate PAR, seedlings of Camptotheca acuminate increased or cut down its midrib angle and petiole angle at the same time. These leaves movement was a kind of adaptive responses of Camptotheca acuminate to different light regimes.