Comparison of Drought Resistance and Photosynthetic Characteristics of Haloxylon ammodendron and Tamarix hohenackeri at Seedling Stage under Different Moisture Conditions

The physiological indices,such as net photosynthetic rate(Pn),transpiration rate(Tr),water use efficiency(WUE),stomatal conductance(Gs),intercellular CO2 concentration(Ci),etc,of Haloxylon ammodendron and Tamarix hohenackeri at seedling stage were studied under field environmental conditions in Moyu county of Xinjiang.Simultaneously their leaf water potential and leaf δ13C ratio were determined.Results showed:(1)The diurnal variation of leaf water potential of Haloxylon ammodendron and Tamarix hohenackeri showed V shape;the daily mean water potential of Tamarix hohenackeri was slightly higher than Haloxylon ammodendron under different irrigation quota;(2) The effects of different irrigation quota on water use efficiency were not significant,but the water use efficiency of Haloxylon ammodendron was higher than Tamarix hohenackeri in the same water treatment;(3) The δ13C value of Haloxylon ammodendron varied in range of-12.65‰～-13.39‰,Tamarix hohenackeri varied in-26.85‰～-27.70‰;water use efficiency of Haloxylon ammodendron was significantly higher than Tamarix hohenackeri(P0.05),this showed the water use efficiency of Haloxylon ammodendron was relatively higher in a long time;(4) Integrated analysis of all the indices by membership function showed drought resistance of Haloxylon ammodendron was higher than Tamarix hohenackeri.