摘要:Water deficits cause significant yield reductions on cultivated lands and greatly restrict crop cultiva-tion aver one-third of the earth's land surface considered as arid or semi-arid (Martinet et al.,2003).since crop plants have limited ability to endure stressful environments in the process of long一term culti-vation. Xerophytes growing in arid regions, however, have evolved various mechanisms to adapt tostzessful environments in the process of long-term evolution. To face the challenge of drought stress,selection of drought一resistant plant species arid characterization of physiological mechanism by whichxerophytes cope with drought stress are, therefore, of great interest.