Abstratc:Ecophysiological traits were compared between two closely related species, Caragana liouana and C.korshinskii in Mu Us sandy land to test their adaptability to local environment.Our results indicated that C.liouana had significantly higher net photosyn-thetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) and intercellular CO2(Ci) than C.korshinskii at high PAR. However, the instantaneous water use efficiency (WUEi) and long term WUE (δ13C) were high in C.korshinskii than those in C.liouana.The Fv′/Fm′, ETR,ΦPSⅡand qP were also significantly higher in C.korshinskii than those in C.liouana, but the qP was not significant.Leaf nitrogen content ( N%) of C.liuo ana was significantly higher than that of C.korshinskii but its nitrogen isotope composition (δ15 N) showed relatively lower values.Overall, C.liouana showed higher Pn by maintaining higher levels of Gs , Tr , Ci and N%, but C.korshinskii showed higher water use efficiency and capacity for nitrogen fixation, light utilization and dissipation, tending to exhibit higher capacity to adapt drought conditions.Those results can support the mechanisms underlying the vicarious distribution of the two species.%本研究比较了生长于毛乌素沙地中间锦鸡儿和柠条锦鸡儿的光合特性、叶片同位素组成以及元素含量等生理生态特征，探讨2种锦鸡儿对毛乌素沙地区域环境的适应性差异。结果表明：中间锦鸡儿的净光合速率（ Pn ）、气孔导度（ Gs ）、蒸腾速率（ Tr ）和胞间CO2浓度（ Ci ）显著高于柠条锦鸡儿，但是瞬时水分利用效率（ WUEi ）和叶片稳定碳同位素（δ13 C）显著低于柠条锦鸡儿；柠条锦鸡儿的PSⅡ有效光化学效率（ Fv′／Fm′）、电子传递速率（ ETR）、 PSⅡ实际光化学效率（ΦPSⅡ）和光化学淬灭系数（qP）在高光强下显著高于中间锦鸡儿；中间锦鸡儿的叶片氮含量（N％）显著高于柠条锦鸡儿，但是稳定氮同位素（δ15 N）却显著低于柠条锦鸡儿。结果说明在毛乌素沙地环境下2种锦鸡儿的主要叶片性状存在明显差异，中间锦鸡儿通过较高的Gs、 Tr 和Ci以及较高的固氮能力维持更高的光合速率，表现出较强的适应性，而柠条锦鸡儿较高的水分利用效率及较强的光能利用能力，有助于其适应更为干旱的生存环境，在一定程度上为理解2种锦鸡儿的地理替代分布机制提供了数据支持。
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