Study On Effects Of Drought Stress On Physiological Characteristics Of Five Tree Species Seedlings

One-year-old seedling of five tree species were potted in Guizhou Normal University and studied to test their characteristics of drought tolerance and to set up an evaluation system,candensis.A drought simulating test had four levels of gradient of water contents which were set up such as:the check(CK) 85%;the slight stress(T1) 75%;moderate stress(T2) 60%and the severe stress(T3)50%.The tree species include the followings:Choerospondias axillaries,Robinia pseudoacacia,Prunus salicina,Cipressus duclouxiana,Toona sinensis.Various morphological, physiological and chemical traits of all species were measured and tested.The test results showed as followings:(1) The leaf area of all seedlings was inhibited under drought stress conditions, and it decreased with the enhancement of drought stress intensity.The ratio of root to stem biomass increased obviously with increasing drought stress intensity.(2) Under the drought stress,the average leaf water content and relative water content in 5 tree species under drought stress turns down step by step,the average leaf of water saturation deficient in 5 tree species under drought stress turns up step by step.Compared with the CK,the average leaf water content decreases 32.6%in the severe stress,the decreases are significantly different(p＜0.05).(3)The leaf cell membrane conductance,MDA content and peroxide enzyme activity of seedlings presented an increasing trend to certain extent with the increase of drought stress.This indicated that the membrane system of seedlings were all damaged.(4)There existed differences in contents of proline,soluble sugar and polyamine related to osmotic adjustment ability among different tree species.Contents of those substances of tree species with high drought tolerance showed an increasing trend. With the enhancement of drought stress intensity and increase of stress period the contents of proline showed a significant increasing trend.Therefore,this index might be available for the evaluation of drought tolerance of tree species.(5) The physiological and biochemical response of the tree species resist-drought is extremely complex,which involves many material complex biochemistry responses.Therefore,many scholars of this field thought that synthesis effect of many kinds of physiological and biochemistry targets,instead of certain physiological and biochemistry index,should be regarded as the evaluation standard of resist-drought.On this study,physiological and biochemistry indexs change of five tree species have been determined under drought stress,combined predecessor's research technique,resist-drought of 5 tree species have been evaluated by Fuzzy Function method.The results are as following:Toona sinensis＞Prunus salicina＞Robinia pseudoacacia＞Choerospondias axillaries＞Cipressus duclouxiana. Evaluation result of the study is consistent with the resist-drought Level summarized via experience,which show that synthesis evaluating method of subordination function is feasible.