辽东楤木光合和蒸腾作用对光照和土壤水分的响应过程

应用CIRAS-2型便携式光合作用系统,测定了不同土壤含水量下辽东楤木光合作用与蒸腾作用的光响应过程,探讨了辽东楤木对光照环境和土壤水分的适应性.结果表明:辽东楤木的净光合速率(P_n)、蒸腾速率(T_r)和叶片水分利用效率(WUE)对光量子通量密度(PFD)的响应过程不同；在强光范围内(PFD 800～1 800 μmol·m^-2·s^-1),随着光强增加,辽东楤木的P_n变化较小,而T_r逐渐减小,WUE明显提高.辽东楤木的光饱和点(LSP)和光补偿点(LCP)分别在800和30 μmol·m^-2·s^-1左右,且受土壤含水量变化的影响较小；但其光合量子效率(Ф)和暗呼吸速率(R_d)受土壤含水量变化的影响较大.辽东楤木的P_n和WUE对土壤含水量的变化有明显的阈值响应,其高效用水的土壤相对含水量(RWC)在44％～79％；在此范围内,辽东楤木能同时获得较高的光合速率和水分利用效率.

Response processes of Aralia elata photosynthesis and transpiration to light and soil moisture.

By using CIRAS-2 portable photosynthesis system, the light response processes of Aralia elata photosynthesis and transpiration under different soil moisture conditions were studied, aimed to understand the adaptability of A. elata to different light and soil moisture conditions. The results showed that the response processes of A. elata net photosynthetic rate (Pn), transpiration rate (Tr), and water use efficiency (WUE) to photon flux density (PFD) were different. With the increasing PFD in the range of 800-1800 micromol x m2(-2) x s(-1), Pn changed less, Tr decreased gradually, while WUE increased obviously. The light saturation point (LSP) and light compensation point (LCP) were about 800 and 30 micromol m(-2) x s(-1), respectively, and less affected by soil water content; while the apparent photosynthetic quantum yield (Phi) and dark respiratory rate (Rd) were more affected by the moisture content. The Pn and WUE had evident threshold responses to the variations of soil water content. When the soil relative water content (RWC) was in the range of 44%-79%, A. elata could have higher levels of Pn and WUE.