Effect Of Drought And Salt Stress On Physiological-biochemical Characteristics Of Sorbus Pohuashanensis Seedlings

Sorbus pohuashanensis,distributed in heilongjiang,jilin,liaoning,neimenggu,hebei,shanxi,gansu,shandong,mostly deciduous trees or shrubs.Fruit color rich,ornamental,edible,medicinal,cultural value.In this experiment,seed seedlings of perennial Sorbus pohuashanensis were used as materials and cultivated in flowerpot.4 gradient treatments under drought stress were set up: soil water content was 80%(control).Soil water content60%(mild stress);Soil water content 40%(moderate stress);Soil water content 20%(severe stress);By CK(0%),0.15%,0.30%,0.45% and 0.60%,5 salt stress gradient,to Chinese catalpa seedling leaf relative water content,photosynthetic characteristics,fluorescence properties and biochemical characteristics of variance analysis and principal component analysis,aims to analyze the Sorbus pohuashanensis under salt and drought stress index of different changes,and Sorbus pohuashanensis in water shortage areas and in saline cultivation to provide certain theoretical basis.The main research results are as follows:(1)Under drought stress,the relative water content of leaves decreased gradually,with a small decrease and a relatively high level under mild and moderate stress.Under severe stress,the decrease amplitude was larger,which indicated that the water retention capacity of the leaves of Sorbus pohuashanensis was decreasing.(2)Under drought stress,net photosynthetic rate and transpiration rate of Sorbus pohuashanensis seedlings decreased gradually,stomatal conductance increased first and then decreased,intercellular carbon dioxide concentration decreased first and then increased.The results indicated that stomatal factors were the main cause of photosynthetic rate decrease in Sorbus pohuashanensis in a short period of time,while non-stomatal factors were the main cause of photosynthetic rate decrease in a long period of time.(3)Under drought stress,the content of soluble protein increased first and then decreased,indicating that osmotic potential was decreased by accumulation of soluble protein in the early stage of stress and osmotic regulation was carried out.However,the self-regulation ability of Sorbus pohuashanensis was inhibited along with the intensificationof stress.The activity of superoxide dismutase and peroxidase increased first and then decreased,indicating that the activity of protective enzyme increased in the early stage of stress.With the increase of stress time,the activity of protective enzyme in the leaves of Sorbus pohuashanensis decreased,and the adaptability to drought decreased obviously.Malondialdehyde content gradually increased,0~16d,under mild and moderate stress,malondialdehyde content in Sorbus pohuashanensis was not significantly increased compared with the control,but significantly higher than the control under severe stress.This was because the cell membrane was seriously damaged due to the increased peroxidation of plant cell membrane,resulting in increased membrane permeability.From 16 to 32 d,severe drought stress increased significantly,significantly higher than control and other stress treatments,indicating that membrane structure and stability were seriously damaged,and membrane was the most damaged.(4)Under drought stress,the initial fluorescence showed an increase trend,and the fluorescence parameters(Fm,Fv/Fm,Fv/Fo)showed a decrease trend.It showed that the drought stress made Sorbus pohuashanensis photosynthesis original reaction,all the damage caused by PS ? damage,leading to a lower ? PS ?,light is restrained or photosynthetic photoelectronic transfer process in the process of impact.(5)Under salt stress,the relative water content of leaves decreased gradually and was lower than 65% under the stress of 0.60%,indicating that the water retention capacity of Sorbus pohuashanensis was weak.(6)Under salt stress,with the intensification of salt stress treatment,the net photosynthetic rate,transpiration rate,intercellular carbon dioxide concentration and stomatal conductance of Sorbus pohuashanensis seedlings decreased.(7)Under salt stress,the content of soluble protein increased first and then decreased,indicating that the osmotic potential could be maintained at a low level in the early stage of stress to protect the cells from damage.However,with the aggravation of salt stress,the tissue or enzyme that synthesized soluble protein in plants became inactivated,thus inhibiting the self-regulation ability of soran.Superoxide dismutase(sod),peroxidase(pod)activity increased first and then,suggests that in the late stress,salt stress increases with time,Sorbus pohuashanensis seedling enzyme activity reduced,leading to Sorbus pohuashanensis leavesin the active oxygen content is higher,and are activated to restrain activity of some enzymes of ros,lead to Sorbus pohuashanensis leaves in the ability to remove oxygen free radicals.Malondialdehyde content increased,salt stress the synthesis of the enzyme system in the early stages of the blade rapidly accumulate,remove excess ros ways to maintain the Sorbus pohuashanensis in the generation of reactive oxygen and removal of dynamic balance,but the content of MDA of Sorbus pohuashanensis seedling leaves did not decline,it could also be a high concentration of salt stress destroyed the plant this balance in the body,increase the content of active oxygen.(8)Under salt stress,the initial fluorescence was gradually increased,and the fluorescence parameters(Fm,Fv/Fm,Fv/Fo)were gradually decreased,and the decrease amplitude was gradually increased with the aggravation of salt stress.This suggests that salt stress to Chinese catalpa tree leaves piece of PS ? produce damage,make PS ?photochemical activity and energy conversion efficiency.The following conclusions are drawn:Sorbus pohuashanensis is suitable to grow under the condition of soil water content of 60-80%.Sorbus pohuashanensis is suitable for cultivation under low salt concentration of less than 0.3%.