Study On Dry And Hot Environmental Stress Resilience Mechanism Of Different Tree Species

The study on Dodonaea viscosa,Eucalyptus camaldulensis,Acacia auriculiformis,E.robusta were conducted to set up 6 kinds of soil moisture gradient and temperature with pot tests to simulate the mechanism of drought and high temperature of dry-hot valley,then the photosynthesis characteristics,the transpiration characteristics,the osmotic adjustment substances,the protective enzyme activity, were analyzed and compared with each other.Also through compared with the field conditions include the photosynthesis characteristics,the transpiration characteristics, the main changes in physiological and biochemical indexes of 4 species were analyzed for vegetation restoration in dry-hot valley of tree species selection and provide a theoretical basis,technical support,the main conclusions were as following:1.Through the light response curves and the CO₂ response curves of 4 species, the net photosynthetic rate(Pn) of 4 species were decreased with the water stress increased,the(Pn) were increased with the rise in CO₂ concentration,at the appropriate water conditions,the high temperature stress can increase the net photosynthetic rate of 4 species.And the respond curves both fitted with the non-rectangular hyperbola,The maximum net photosynthetic rate(Pmax) of Dodonaea viscosa reached 15.208μmolCO₂·m^-2·s^-1 at 40℃and appropriate water condition,the Pmax of Eucalyptus camaldulensis reached 15.768μmolCO₂·m^-2·s^-1,at 30℃and appropriate water condition,the Pmax of Acacia aurivuliformis and E. robusta.were 15.699μmolCO₂·m^-2·s^-1,and 12.249μmolCO₂·m^-2·s^-1,at 40℃and appropriate water condition.The leaf-air temperature difference of 4 species and photosynthetic active radiation was a significant positive correlation,but with the temperature and water stress increased,its decline in relevance.2.The transpiration rate at 40℃increased with the water stress got worse,at 30℃the moderate water stress can increase the transpiration rate of 4 species;Acacia auriculiformis was affected most obviously by water stress,and Dodonaea viscose, E.robusta maintain a high transpiration rate. 3.The water use efficiency was significantly inhibited by high temperature:As the temperature increased,the water use efficiency declined.Leaf relative water content became high when temperature dropped or water stress got worse.Leaf relative water content of Acacia auriculiformis reduced most obviously,while that of Dodonaea viscose,E.robusta,E.camaldulensis didn't decline significantly.4.The 4 species adjusted the proline content and the activity of protective enzyme to cope with environmental stress.The proline content,malondialdehyde content and antioxidant enzyme levels would ascend when temperature and water stress became serious,the Electric Conductivity rose with temperature and water stress.5.Through principal component analysis,4 tree species at different moisture and temperature combinations,the main physiological and biochemical indexes anti-dry and heat is not in the same ways,but 4 species were all to reduce the photosynthetic rate,enhance water regulation,changes in membrane permeability,to enhance the activity of antioxidant enzymes,a comprehensive response to the dry-hot environment stress of dry-hot valley.