Dynamic Physiological Mechanism Of Haloxylon Ammodendron Responding To Various Degrees Of Modeling Drought Stress

Water is one of the scarcest resources in the arid desert area,if only depend on irrigation to meet the demand of plant,which will reduce feasibility of the large-scale restoration of desert vegetation and ecological rebuilding.Only the use of biological control,merely from the perspective of relying on natural rainfall that can build group and maintain the survival of the desert xeric plants,through the establishment of artificial desert vegetation and increasing coveration of surface plant and weakening the wind erosion,improving the ecological environment of soil and ground,at the same time,increasing the species richness,then to form the new community adapting to local ecology successionally.we can fundamentally realize the ecological reconstruction in desert area and curb the desertification of limited available land resources,on the basis of this can we reduct the effect of drought on crop yield.The Haloxylon ammodendron is the unique small arbors with super anti-inverse in desert area,having a strong natural resistance to drought,high temperature,cold and barren stress,so we take it the preferred species for forestation sand in desert area.Therefore,we aims to investigate dynamic response mechanism of the Haloxylon ammodendron for different degrees of drought stress simulated.This study conducts a series of system researches to physiological and biochemical indexes of the different degrees of simulated drought stress of Haloxylon ammodendron,such as,organic solutes?Na+ and K+ contents.protective enzyme activity and so on.The main results are as follows:1.The shoot water content was unaffected under mild modeling drought stress(-0.5MPa),while moderate(-0.75MPa)and severe(-l.OMPa)modeling drought stresses significantly reduced shoot water content,indicating that the seeding of H.ammodendron can adapt to mild modeling drought stress through its own regulatory mechanism.The osmotic potential decreased continuously since 6 hours after the three levels of modeling drought stresses.2.With the prolonging of treatments,the contents of free proline,betaine,soluble sugar and soluble protein rose sharply,but the rate of increase was different.They may work toghter to resist for drought.The contribution of organic solutes to osmotic potential was betaine>soluble sugar>soluble protein>free proline.3.Shoot Na+ content increases sustainably with treating time but the increasing rate varies with the degree of stress:under mild stress,Na+ content starts to be significantly higher than control from 48h,while under moderate and severe stresses,start from 6h,indicating drought stress would promote uptake to Na+.The content of K+ was stable,comparing to control in all process.However,the aboveground Ca2+ content all have no significantly changes compared to control.The contribution of in Na+ to osmotic potential was greater than K+.4.The peroxidation of membrane lipid was enhanced by modeling drought stress.48 hours after mild drought stress,membrane permeability increased signifciantly compared to control.5.With prolonging of treatment time,the trend of protective enzyme activity rose in all drought stress.SOD and POD activity incresed rapidly in 6 hours later.But the CAT activity increased significantly after 24 hours.The above results showed that the osmotic regulation and protective enzyme system play important roles for H.ammodendron adapting to drought stress.