遮光对红鳞蒲桃幼苗光合特性的影响

为了解红鳞蒲桃（Syzygium hancei）对光能的需求及适应性，以红鳞蒲桃幼苗为材料，设置透光率分别为100.0%、72.3%、48.6%、24.9%的4种光照处理，测定其光合作用参数、光响应参数、叶绿素含量等数据，研究不同遮光处理对其光合特性的影响。结果表明：（1）红鳞蒲桃是喜光树种，红鳞蒲桃幼苗净光合速率（Net Photosynthetic Rate，P_n）、气孔导度（Stomatal Conductance，G_s）日均值随着遮光程度的增加而减小，胞间CO₂浓度（Intercellular Carbon Dioxide Concentration，C_i）日均值随之增大，过度遮光下（透光率为48.6%和24.9%），蒸腾速率（Transpiration Rate，T_r）日均值显著低于全光照；（2）遮光条件下，红鳞蒲桃幼苗净光合速率下降可能是非气孔限制引起的；（3）红鳞蒲桃幼苗的最大净光合速率（Maximum Net Photosynthetic Rate，P_max）、光补偿点（Light Compensation Point，LCP）、光饱和点（Light Saturation Point，LSP）、暗呼吸速率（Respiration Rate，R_d）均随着光照强度的增加而显著增加；（4）红鳞蒲桃幼苗叶绿素a、叶绿素b及叶绿素（a+b）的含量均随着遮光程度的增加而显著增加，叶绿素a/b的值随之减小。红鳞蒲桃在幼苗期具有较明显的喜光性，因此，在红鳞蒲桃幼苗的培育及种群的恢复过程中，可通过疏伐、修剪枝条等措施来增加林内的透光量，为处于幼苗时期的红鳞蒲桃创造适宜的光照环境，为其自然更新提供良好条件。

Effects of Shading on Photosynthetic Characteristics of Syzygium hancei Seedlings

In order to explore the demand and adaptability of Syzygium hancei to light energy,the seedlings of S.hancei were used as materials,and 4 light treatments with transmittance of 100.0%,72.3%,48.6%,and 24.9% were set up to measure the photosynthetic parameter,light response parameter and chlorophyll content.In addition,the effects of different shading treatment on photosynthetic characteristics were analyzed.The results showed that: (1) S.hancei was a light-loving tree.The daily mean values of Net Photosynthetic rate (P_n) and Stomatal Conductance (G_s) of S.hancei seedlings decreased with the increase of shading degree,and the daily mean value of Intercellular Carbon Dioxide Concentration (C_i)increased.The daily mean value of Transpiration Rate (T_r) under excessive shadings (48.6%,24.9%) was significantly lower than under full sunlight.(2) Under shading conditions,the decrease of net photosynthetic rate in S.hancei might be caused by non-stomatal restriction.(3) With the increase of light intensity,Maximum Net Photosynthetic Rate (P_max),Light Compensation Point (LCP),Light Saturation Point (LSP),Respiration Rate (R_d) of S.hancei seedlings all increased significantly.(4)With the increase of shading degree,the contents of chlorophyll a,chlorophyll b and chlorophyll (a+b) in S.hancei seedlings increased significantly,and the value of chlorophyll a/b decreased accordingly. S.hancei has obvious light-loving feature at the seedlings stage.Therefore,during the process of seedling cultivation and population restoration,measures such as thinning and pruning can be taken to increase the amount of light transmission in the forest and create suitable light environment for the S.hancei at seedling stage and provide a good light environment for its natural regeneration.