Physiological And Biochemical Response Of Xanthoceras Sorbifolia Bunge To Drought And Salt Stress At Seedling Stage

Saline-alkali soil is often accompanied by drought,which cause challenges and have varying effects on the physiology and growth of plants.In this paper,Xanthoceras Sorbifolium Bunge seeds and 2-year-old Xanthoceras Bunge seedlings were treated with 15%PEG6000 respectively,in order to study the effects of drought and salt stress on salt tolerance physiological and biochemical characteristics of Xanthoceras sorbifolia Bunge seedlings,the physiological and biochemical indicators of leaf morphology,leaf organic osmotic adjustment system,antioxidant protective enzyme system,photosynthetic system,inorganic ion concentration,membrane system and root activity were studied under 15%concentrated PEG6000 and different concentrations(0,50,100,150 mmol·L-1)、(0%,0.25%,0.35%,0.45%)of salt(NaCl)stress treatment.The mechanism of drought and salt tolerance of Xanthoceras sorbifolia Bunge was discussed to provide certain theoretical support for the growth of rational cultivation in saline-alkali soil.we can draw the following conclusions from the research:1.Under the low salt concentration(≤50 mmol·L-1 NaCl),the salt resistance of Xanthoceras sorbifolia Bunge seedlings pretreated with 15%concentrated PEG6000 seeds increased.The soluble sugar,soluble protein,superoxide dismutase(SOD)activity,sodium ion(Na+)content of seedlings leaves of Xanthoceras sorbifolia Bunge pretreated with 15%PEG6000 at low salt concentration(≤50 mmol·L-1 NaCl)were significantly lower than without PEG6000 pretreatment;net photosynthetic rate(Pn),stomatal Conductance(Cond),intercellular carbon dioxide concentration(Ci),transpiration rate(Tr),maximum photochemical efficiency(Fv/Fm)and Potassium ion(K+)content were significantly higher than without PEG6000 pretreatment.2.With the increase of the degree of salt stress,the soluble sugar,proline,relative conductance,malondialdehyde(MDA),soluble sugar,proline and sodium ion(Na+)content seedlings leaves of Xanthoceras sorbifolia Bunge pretreated with 15%PEG6000 showed an increasing trend;while the soluble protein,superoxide dismutase and peroxidase(POD)all showed a trend of rising first and then decreasing,and the each index was the highest at a concentration of 100 mmol·L-1;Net photosynthetic rate(Pn),stomatal conductance,intercellular carbon dioxide concenTration,transpiration rate,maximum photochemical efficiency,potassium ion all showed a downward trend.Regardless of whether it was pretreated with 15%PEG6000,its seedlings had the highest salt damage level at 150 mmol·L-1NaCl concentration,which was moderate salt damage.3.At the low salt concentration(≤0.35%NaCl),the salt tolerance of seedling could be improved after 15%concentrated PEG6000 treatment.The soluble sugar,soluble protein,proline,superoxide dismutase activity,peroxidase,sodium ion content,the relative conductance,malondialdehyde of 2-year-old seedlings leaves of Xanthoceras sorbifolia Bunge pretreated 15%PEG6000 were lower than those without PEG6000;net photosynthetic rate,stomatal Conductance,intercellular carbon dioxide concentration,transpiration rate,maximum photochemical efficiency,Chlorophyll a,chlorophyll b,root activity and Potassium ion content were significantly higher than without PEG6000 pretreatment.At 0.45%NaCl concentration,the damage degree of seedlings treated with 15%PEG6000 was higher than that of seedlings not treated with PEG6000,and the damage grade belonged to severe salt damage.4.Under drought and salt cross stress,with the increase of salt concentration and the extension of stress time,physiological indexes such as soluble sugar,proline,soluble protein,sodium ion content,relative conductance,malondialdehyde content,superoxide dismutase activity,peroxidase in leaves of 2-year-old Xanthoceras sorbifolia Bunge all showed different degrees of increase;the contents of soluble sugar,soluble protein and enzyme activity increased first and then decreased with the extension of the stress time,the other indicators except potassium which decreased showed an upward trend;net photosynthetic rate,stomatal Conductance,intercellular carbon dioxide concentration,transpiration rate,chlorophyll a,chlorophyll b,maximum photochemical efficiency,root activity and other indicators showed a downward trend with the increase of salt concentration.The higher the salt concentration,the greater the change.The content of potassium ion content showed a downward trend with the increasing of stress degree and the extension of stress time,and there were significant differences among various physiological and biochemical indexes and different stress days.In the first 16 days of stress,the range of change is large,and then the change is small and tends to be stable.5.In the study,Xanthoceras sorbifolia Bunge seedings showed a significant cross-reactivity against adversity.Under low salt concentration,appropriate drought treatment at 2-year-old seedlings stage can improve the salt-resistance.When the salt concentration exceeds the tolerance range of the seedlings,drought would aggravate considerablely the degree of salt damage.After the seeds of Xanthoceras sorbifolia Bunge were pretreated with 15%PEG6000,the salt tolerance of seedlings was also improved.