梭梭与白梭梭气体交换特征对比分析

梭梭WTBX](Haloxylon ammodendron)与白梭梭(H.persicum)WTBZ]是古尔班通古特沙漠植物群落2个最主要的建群种。通过对梭梭与白梭梭光合特性及相关环境因子的同期观测，探讨其光合响应特征及其与环境因子关系的异同。结果表明：梭梭对弱光的利用能力大于白梭梭，而白梭梭利用强光的能力大于梭梭。梭梭和白梭梭净光合速率WTBX](Pn)、气孔导度(Gs)、蒸腾速率(Tr)的日变化特征均为“单峰”型，但Pn、Gs峰值出现时间略有差异，Tr的峰值出现时间为16:00。根据梭梭和白梭梭Pn、胞间WTBZ]CO2浓度WTBX](Ci)及气孔限制值(Ls)的变化方向，推测梭梭光合“午休”主要由气孔因素引起。白梭梭日平均Pn、Tr和WUE（水分利用效率）均高于梭梭，说明白梭梭是一种高光合、高蒸腾、高水分利用效率的物种。相关分析表明，对梭梭、白梭梭的Pn影响最显著的环境因子是光量子通量密度(PPFD)。

Gas Exchange of Haloxylon ammodendron and H. persicum

Haloxylon ammodendronWTBZ] and WTBX]H.persicumWTBZ] are two main edificators in the Gurbantonggut Desert, Xinjiang. Based on the simultaneous observations of photosynthetic characteristics and related environmental factors affecting the growth of H.ammodendron and WTBX]H.persicumWTBZ], different photosynthetic responses of the two species to environmental factors were studied. Results showed that H.ammodendron was better in using lowlight than WTBX]H.persicumWTBZ], but it was contrary in using highlight. The curves of daily variation of net photosynthetic rate, stomatal conductance and transpiration rate were all unimodal, the time of occurring the peak values of net photosynthetic rate and stomatal conductance was slightly different, and the peak value of transpiration rate occurred always at 16:00. According to the variation of photosynthetic rate, intercellular CO2 concentration and stomatal limitation of H.ammodendron and WTBX]H.persicumWTBZ], it was considered that the “midday depression” of photosynthesis was mainly caused by stomatal factors. The daily averages of photosynthetic rate, transpiration rate and water use efficiency of WTBX]H.persicumWTBZ] were higher than those of H.ammodendron. Correlation analysis revealed that the photon flux density was the most significant environmental factor affecting the photosynthetic rate of H.ammodendron and WTBX]H.persicumWTBZ].