Effect of Shading on Physiological and Ecological Characteristics of Osmanthus fragrans

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.