紫外线B增强对滇杨、 川杨光合参数及暗呼吸的影响

在自然条件下利用紫外灯补充紫外线B,模拟臭氧层破坏10%、20%后昆明地区增加的紫外线B强度2.5和5 kJ/(m2d),研究了紫外线B增加对滇杨(Populus yunnanensis)(2 430 m)和川杨(P.szechuanica)(3 300 m)光合参数、暗呼吸速率、叶片厚度的影响。结果表明:与对照相比,2.5和5 kJ/(m2d)紫外线B处理使滇杨的净光合速率(Pn)分别降低了32%和51%,川杨则降低了16%和39%;相反,2.5和5 kJ/(m2d)紫外线B显著提高了暗呼吸速率(Rd)和叶片厚度;相关性分析表明:两种杨树的叶片净光合速率与水分利用效率均呈显著正相关,与暗呼吸速率呈显著的负相关(P0.01)。此外,2.5 kJ/(m2d)紫外线B强度对滇杨和川杨的气孔导度、暗呼吸速率及其与净光合效率比值的影响不同;且川杨的净光合速率、暗呼吸速率、叶片厚度都显著大于滇杨,这些差异反映出生长在高海拔环境下的川杨比生长在低海拔的滇杨对紫外线B增强具有更强的耐性。

Effects of Enhanced UV-B Radiation on Photosynthetic Parameters and Dark Respiration of Populus yunnanensis and P.szechuanica

We compared the leaf photosynthetic parameters, dark respiration rate and leaf thickness of Populus yunnanensis and P. szechuanica originating from altitudes of 2 430 m and 3 300 m,respectively,when exposed to enhanced ultraviolet-B (UV-B) radiation: 2.5 and 5 kJ/(m2d). These enhanced UV-B intensity were provided by ultraviolet lamp based on simulation of 10% and 20% ozone depletion in Kunming area. Results showed that enhanced UV-B radiation significantly reduced Net photosynthetic rate (Pn) by 32% and 51% in P. yunnanensis, by 16% and 39% in P. szechuanica, respectively. In contrast, dark respiration rate (Rd) and leaf thickness of both species were significantly increased. Correlating analysis indicated that there were significantly positive correlation between Pn and WUE, and negative correlation between Pn and Rd (P0.01).On the other hand, 2.5 kJ/(m2d) UV-B treatments had different influences on stomatal conductance, Rd and Rd/Pn of both study species.Moreover, Pn,Rd and leaf thickness were significantly larger in P.szechuanica than in P.yunnanensis. Therefore,it could conclude that P.szechuanica from high altitude had a greater tolerance to enhanced UV-B environment than P.yunnanensis from low altitude.