Abstract: It is important to understand the photosynthetic process of Haloxylon ammodendron growing in the hinterland of the Lop Nur and its adaptation to environment. In this study,the photosynthetic characteristics and response of planted H.ammodendron to drought stress were revealed,and a suitable irrigation period was established.Three drought treatments were designed: i.e.the slight,moderate and heavy drought treatments.The results are as follows: ① Under heavy drought,LCP and LSP of H.ammodendron were 118.75 μmol·m^-2·s^-1 and 6174.79 μmol·m^-2·s^-1 respectively,which were the largest use of light energy in these three treatments.It means that,in an adverse environment,H.ammodendron expanded the scope of available light energy to improve the efficiency of using environmental resources; ② In the slight and moderate drought treatments after irrigation,the Pnmax values of H.ammodendron were 35.06 μmol·m^-2·s^-1 and 49.51 μmol·m^-2·s^-1,increased by 48.81% and 22.83%,respectively,and higher than those in drought.It could be seen that water supply is an important factor affecting plant growth in this region; ③ There was a long-duration midday depression of photosynthesis of H.ammodendron under drought stress,which might be an adaption to environment; ④ The difference of daily photosynthetic process between slight and moderate drought treatments was not significant,and the physiological indexes of photosynthesis were rapidly increased after irrigation.Considering to saving water,the moderate drought is the most suitable irrigation schedule.

Key words: Haloxylon ammodendron, drought stress, photosynthesis, water use efficiency, Lop Nur Hinterland