Abstract:Reaumuria soongorica and Zygophyllum xanthoxylum are very important ultra-xeromoph shrubs in the northwest arid desert region of China. Seeds of the two species were collected at maturity in the Alashan aria desert grassland of China in 2001 and kept at -5℃ until use. Responses of seed germination to simulated drought stress (germination paper moistened by PEG 6000 solution) and sowing depths were investigated in this study. The drought stress included 10 treatments ranging from 0 to -2.7MPa, and sowing dep...