Abstract: This paper studied the water regulation characteristics and stress resistance of Caragana opulens population in Helinger (semi-arid area) and Alashan (intensively arid area),aimed to understand the adaptation mechanisms of this population to arid environment.The results showed that compared with Helinger population,Alashan population had a higher content of osmotic adjustment substances in leaf cells,which resulted in a lower osmotic potential,and thus,stronger osmotic adjustment ability.The leaf water and free water contents of Alashan population were lower than those of Helinger population,while the bound water content and the ratio of bound water to free water of the former were higher than those of the latter.The leaf water potential of Alashan population was lower than that of Helinger population.Alashan population had a lower stomatal conductance than Helinger population,indicating that the former had stronger water adjustment ability.The malondialdehyde (MDA) content of Alashan population was higher than that of Helinger population,while the permeability of plasma membrane and the super-oxygen free radicals content of Alashan population were lower than those of Helinger population.It was suggested that Alashan population had a stronger ability in removing free radicals,and a higher stability of plasma membrane. C.opulens could adapt to arid environment through effective water adjustment and strong stress resistance.

Key words: Vegetation, Climate, GIS, Inner Mongolia