遮阴对四季桂生理生态特性的影响

Effect of Shading on Physiological and Ecological Characteristics of Osmanthus fragrans

摘要:

为了解遮阴对四季桂（Osmanthus fragrans）生长的影响，研究了成都地区夏季遮阴处理下四季桂扦插苗生理生态特性的变化。结果表明，随遮光率增加，比叶重下降；叶绿素b（Chl b）含量增加，Chl a/b降低。遮阴下叶片可溶性糖、可溶性蛋白含量降低，以80%遮光率下降的最显著；随遮光率上升，叶片丙二醛（MDA）含量下降，超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性降低，以55%、80%遮光率的MDA含量下降显著。遮阴处理下，叶片光饱和点（LSP）、光补偿点（LCP）、最大净光合速率（P_max）、暗呼吸速率（R_d）均下降，而表观量子速率（AQE）增大；瞬时光能利用率（LUE）升高，净光合速率（P_n）、气孔导度（Gs）、气孔限制值（Ls）均降低，胞间CO₂浓度（Ci）升高。四季桂幼苗主要通过提高P_n和抗氧化酶活性来适应强光环境；降低SLW、LSP、LCP和R_d，提高Chl和Ci含量，增大AQE和LUE提高弱光利用能力，中度遮阴（25%、55%遮光率）有利于幼苗在夏季的生长。

Abstract:

In order to understand the effect of shading on growth of Osmanthus fragrans, the changes in physio- ecological characters of three-year-old O. fragrans seedlings in summer were studied under shading in Chengdu. The results showed that the specific leaf weight decreased, chlorophyll b content increased, but the chl a/b was reduced with increment of shading rate. The soluble sugar and soluble protein contents in leaf decreased under shading, while those had the most significant effect under 80% shading. Malondialdehyde (MDA) content in leaf reduced, catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) activities decreased with increasing of shading rate, and MDA content decreased significantly under 55%-80% shading. The light saturation point (LSP), light compensation point (LCP), maximum net photosynthetic rate (P_max) and dark respiration rate (R_d) all decreased, but the apparent quantum effciency (AQE) increased under shading. Otherwise, instantaneous light energy utilization (LUE) increased, net photosynthetic rate (P_n) and stomatal conductance (Gs) decreased, inversely intercellular CO₂ concentration (Ci) increased with the shading rate increment. Therefore, the seedlings of O. fragrans could adapte to strong light environment by improving P_n and antioxidant enzyme activities; enhance weak light utilization ability by decreasing SLW、LSP、LCP and R_d, and increasing chlorophyll content, Ci and AQE, LUE. So, it could grow better under moderate shading (25% and 55% shading rate) in summer.