地下水埋深对胡杨(Populus euphratica)、柽柳(Tamarix ramosissima)气孔响应水汽压亏缺敏感度的影响

Stomatal Sensitivity to Leaf-to-air Vapor Pressure Deficit of Populus euphratica and Tamarix ramosissima under Contrasting Groundwater Conditions

通过调节LI-6400光合测定系统叶室内相对湿度,测定了高地下水埋深和无地下水条件下胡杨(Populus euphratica)、柽柳(Tamarix ramosissima)叶片气孔导度(Gs)对水汽压亏缺(LVPD)变化的响应,并线性拟合得到Gs对LVPD响应的敏感度。结果表明:高地下水埋深条件下,胡杨Gs对LVPD的敏感度显著高于柽柳(P<0.05),无地下水条件下两物种Gs对LVPD的敏感度差异不显著(P>0.05);高地下水埋深条件下胡杨Gs对LVPD的敏感度高于无地下水条件(P<0.05),柽柳则差异不显著(P>0.05)。胡杨高地下水埋深条件下较高的气孔敏感度说明该物种在有利水分条件下水分利用偏于保守。无地下水条件下柽柳气孔敏感度基本不变,Gs下降幅度较小,而胡杨气孔敏感度与Gs均大幅度下降,两物种净光合速率(Pn)呈现相应变化,表明胡杨Pn更容易受环境水分亏缺的约束,在植物-水分关系层面柽柳表现出对水分条件多变、大气蒸腾压力高的荒漠河岸生境更优的适应能力。

Using portable photosynthesis system（LI-6400）,we measured leaf conductance of Populus euphratica and Tamarix ramosissima grown under conditions with high groundwater and without groundwater availability to explore their stomatal sensitivity in response to changes in leaf-to-air vapor pressure deficit（LVPD）,which were obtained by regulating the relative humidity in the chamber in our experiment.Stomatal sensitivity to LVPD was calculated by fitting the linear relationship between stomatal conductance（Gs）and ln-transformed LVPD.The results indicate that the stomatal sensitivity to LVPD for P.euphratica was significant higher than T.ramosissima under high groundwater availability while similar under no groundwater condition.Under no groundwater condition,P.euphratica showed significantly reduced stomatal sensitivity to LVPD,while similar for T.ramosissima,in comparison to high groundwater condition.Thus the higher stomatal sensitivity to LVPD under high groundwater condition indicates that P.euphratica is relatively conservative in water use when environmental water supply is favorable.In contrast,T.ramosissima exhibited an inert stomatal response to LVPD,a small reduction in Gsand a parallel Pn when no groundwater was available,which suggest that P.euphratica is more susceptible to environmental water deficit,and from aperspective of plant-water relation,T.ramosissima exhibits advantages in adapting to the desert riparian zones characterized by highly variable water environment and great transpirational demand.