Studies on Seedling Photosynthetic Characteristics of Five Tree Species under Drought Stress

In order to provide theoretical basis for vegetation restoration in rocky desertification district,the seedlings of 5 tree species,Dodonaea viscosa( Linn.) Jacq.,Fokienia hodginsii( Dunn) Henry et Thomas,Platycladus orientalis( Linn.) Franco,Zanthoxylum bungeanum Maxim,and Cinnamonum camphora L. with same age in the district were used as study objects,through potted water control experiments,to measure and calculate the chlorophyll content,net photosynthetic rate,transpiration rate,stomatal conductance,intercellular CO2concentration, water use efficiency,and some other physiological and ecological index,and the adaptabilities and differences among the 5 tree species under different moisture gradients were compared. The results are as follows.( 1) With the increasing drought stress,the chlorophyll content of 5 tree species changed in different levels,D. viscosa showed a trend of gradually reducing,P. orientalis and F. hodginsii showed a trend of decrease and then increase,while Z. bungeanum and C. camphora showed a trend of increase and then decrease;( 2) The physiological and ecologicalparameters expressed different variation: the net photosynthetic rate,transpiration rate,and stomatal conductance showed decreasing trends,and under moderate and severe drought stress,they reduced significantly,the net photosynthetic rate of P. orientalis decreased by 100. 5%,which was the sharpest decline under severe drought stress; the intercellular CO2concentration dropped under mild drought stress,while increased under moderate and severe drought stress; the water use efficiency increased under mild and moderate drought stress,but decreased under severe drought stress; the water use efficiency of C. camphora decreased under severe drought,but still 1. 05 times that of the contrast.( 3) Based on a comprehensive analysis of the physiological and ecological indexes,it showed that all the seedlings could tolerate a certain degree of drought stress,belonging to the stronger drought-resistant ability trees,but the water control drought tolerance ability of C. camphora was higher than that of the other 4 species and is more capable to adapt to environment of rocky desertification district.