克里雅河流域荒漠-绿洲交错带3种不同生活型植物的光合特性

利用LI-6400光合仪测定新疆克里雅河流域荒漠-绿洲交错带自然生长的芦苇、柽柳、胡杨叶片的气体交换参数及环境影响因子,通过对比3种植物光合特性的差异及其与环境因子间的关系,探讨3种植物对荒漠环境的适应特性和机制。结果表明:(1)3种植物叶片Pn日变化均呈不对称的双峰曲线,"午休"现象明显,Pn日均值的大小依次为胡杨芦苇柽柳,种间差异不显著。(2)Tr、PAR和Gs与3种植物Pn的日变化存在极显著或显著的相关关系,其中影响芦苇Pn的主要因子是Tr、PAR和Gs,作用效应为TrGsPAR;影响柽柳Pn的主要因子是Tr、Gs,作用效应为TrGs;影响胡杨Pn的主要因子是Tr。(3)3种植物的光合作用对光强和CO2的响应特征可用二次方程描述;光补偿点和饱和点均为柽柳胡杨芦苇;CO2补偿点为胡杨柽柳芦苇,饱和点为胡杨芦苇柽柳。(4)3种植物的表观量子效率在0.0341—0.0411 mol/mol之间,羧化效率在0.0480—0.0546 mol m-2s-1之间。综合比较表明,3种干旱区植物在自然条件下日均净光合速率、光能利用率和CO2同化能力差异不显著,气孔限制是光合"午休"现象产生的主要原因;影响3种植物光合作用的主导因子各不相同,但Tr与Pn间的关系较其它因子更为密切。

Photosynthetic characteristics of three different life-form plants in the desert-oasis ecotone of Keriya River Basin

Vegetation plays an important role in preventing wind erosion, sand fixation, water conservation and ecosystem restoration in oasis ecosystem. For the photosynthetic characteristics could fairly reflect the adaptation of plants to their habitat, gas exchange parameters and environmental factors of three different life-form plants which grown in the desert-oasis ecotone of Keriya River Basin were measured. By comparing the photosynthetic characteristics of Phragmites australis, Tamarix ramosissima, Populus euphratica and their relationship with environmental factors, adaptive capacities and mechanisms of the three different life-form plants were discussed. The results were as follow: The diurnal variation in net photosynthetic (P_n) rate of the three plants showed two peaks, which displayed remarked photosynthetic "midday depression". The order of the average values of P_n was: P. euphratica > P. australis > T. ramosissima. However, there was no significant difference among them. The analysis of partial correlation and path on P_n and environmental factors showed that the diurnal variation of P_n had significant correlation with transpiration rate (T_r), photosynthetically active radiation (PAR), and stomatal conductance (G_s), respectively. T_r, PAR and G_s were the main factors which affected P_n of P. australis and the order of effecting ability was T_r > G_s > PAR. T_r, and G_s were the main factors which affected P_n of T. ramosissima and the order of effecting ability was T_r> G_s. T_r was the only main factor which affected P_n of P. euphratica. For the three kinds of plants, the P_n-PAR response curves and P_n-CO₂ response curves had the same changing tendency, which could be quantitatively described by quadratic equation, respectively. The order of light compensation points and light saturation points were both T. ramosissima > P. euphratica > P. australis. The order of carbon dioxide compensation points was P. euphratica > T. ramosissima > P. australis and the order of saturation points were P. euphratica > P. australis> T. ramosissima. The apparent quantum yield and carboxylation efficiency of these three plants were varied from 0.0341 to 0.0411 mol/mol and 0.0480 to 0.0546 mol m^-2 s^-1 on daily basis, respectively. The results indicated that the average net photosynthetic rate, energy efficiency and CO₂ assimilation capacity were not significantly different among the three kinds of plants, and the photosynthetic "midday depressions" was mainly resulted from stomatal limitation. The main factors which affected physiological process of photosynthesis are different among the three different life-form plants, but the relationship between T_r and P_n is closer than other factors.