Effects of Shading on Physio-ecology Characteristics of Bischofia javanica Seedlings

Abstract:

In order to understand the effect of shading on growth of Bischofia javanica seedlings,the changes in physio-ecology characteristics of one-year-old Bischofia javanica seedlings were studied under different shading in summer,including 100% NS (nature sunshine),41.3% NS,14.6% NS and 3.6% NS for 150 days.The results showed that the light compensation point (LCP),light saturation point (LSP),dark respiration rate (Rd) increased with the increment of shading degree,and apparent photosynthetic quantum yield (AQY) increased continuously.The noon break phenomenon was obvious from the daily changes in net photosynthetic rate (Pn),stomatal conductance (Gs),intercellular CO₂ concentration (Ci) and transpiration rate (Tr) of B.javanica seedlings under different light conditions.The decreasing of photosynthetic rate was due to non-stomatal factor under shading,while that was to stomatal factor under whole sunshine.Along the increment of shade degree,the contents of chlorophyll and soluble sugar in B.javanica seedlings increased at first and then decrease,on the contrary of the relative conductance rate,malondialdehyde (MDA) content and CAT activity with the minimum values under 41.3% NS.The SOD activity and soluble protein content decreased with increment of shading degree.Therefore,the B.javanica seedlings would adapt to strong light environment by improving the Pn,antioxidant enzyme activities (SOD and CAT) and chlorophyll content,reducing LSP,LCP and Rd,increasing the AQY.It could grow better under moderate shading (41.3% NS) in summer.