胡杨叶片气孔导度特征及其对环境因子的响应

Stomatal Conductance Characteristics of Populus euphratica Leaves and Response to Environmental Factors in the Extreme Arid Region

依据2005年对极端干旱区荒漠河岸林胡杨的观测资料,对胡杨气孔运动进行了分析研究以揭示胡杨的水分利用特征与抗旱机理。结果表明:(1)胡杨叶片气孔导度日变化呈现为周期波动曲线,其波动周期为2 h,傍晚(20:00)波动消失;净光合速率和蒸腾速率与气孔导度的波动相对应而呈现同步周期波动。(2)胡杨的阳生叶气孔导度高于阴生叶,且不同季节气孔导度值不同,阳生叶气孔导度的季节变幅大于阴生叶。(3)胡杨气孔导度与气温、相对湿度和叶水势有显著相关关系,当CO2浓度较小时,胡杨气孔导度随CO2浓度的增加而增加,当CO2浓度达到一定值后气孔导度不再增加,反而随CO2浓度的增加大幅度降低。(4)胡杨适应极端干旱区生境的气孔调节机制为反馈式反应,即由于叶水势降低导致气孔导度减小,从而减少蒸腾耗水,达到节约用水、适应干旱的目的,表明胡杨的水分利用效率随气孔限制值的增大而减小,二者呈显著负相关。

According to the observed data of Populus euphratica which growing in extreme arid environment in 2005,the gas exchange characteristics of P. euphratica were studied under natural condition by using a portable Li-6400 photosynthesis system. The results showed that：the oscillations of stomatal conductance in P. euphratica leaves took place in the diurnal course in hot and bright sunny day with an oscillation periodicity of about 2 h, and disappeared after 20.00. The assimilation and transpiration, associated with stomatal conductance,exhibited and sustained oscillations in the diurnal course simultaneously. Stomatal conductance is higher in leaves of sunny positions than that of shade positions of P. euphratica. Stomatal conductance of P. euphratica has significant correlation with temperature, relative humidity and leaf water potential. When CO2 concentration is lower, the stomatal conductance of P. euphratica increment with the CO2 concentration rises. However, when CO2 concentration attained a certain value, the stomatal conductance was no longer increase. If CO2 concentration continued to goes up, the stomatal conductance would significantly reduces with the COz concentration rising. It was feedback manner that mechanism of stomatal adjustment of P. euphratica adapting habit of extreme arid region,namely to fall leaf water potential cause stomatal conductance to decrease, which reduced water consumption from transpiration to save water and adapt drought. Water utilization efficiency （WUE） of P. euphratica increased with stomatal limitation value decreasing,vice versa,it will increase. These results provided scientific basic for understanding drought resistan t mechanism and improving water utilization efficiency of P. euphratica.