| Drought is one of the factors that restrict the productivity of forest ecosystem in semi-arid area,and the large-scale distribution of high-calcium soil in this area is another important environmental factor affecting forest growth.Ectomycorrhizal fungi can enlarge the area of water and nutrient uptake and improve plant stress resistance.In this study,the effects of drought and high calcium on the growth and physiology of Quercus acutissima seedlings and the effects of ectomycorrhiza on the adaptation of Q.acutissima to water and calcium stress were analyzed,and the ecological significance of ectomycorrhiza was further clarified.The main results of this study are as follows:(1)Both drought and high calcium treatment inhibited the growth of Q.acutissima seedlings.Compared with drought treatment,high calcium and high-calcium-drought treatment significantly inhibited the growth of Q.acutissima seedlings.Ectomycorrhiza could alleviate the inhibition of growth under various stresses,but only effects on stem biomass,height and diameter under high calcium treatment and stem biomass under high-calcium-drought treatment were significant.(2)The concentration of soluble sugar,starch and NSC in other organs of Q.acutissima seedlings were increased under drought treatment except that soluble sugar concentration in roots were decreased slightly.High calcium and high-calcium-drought treatment reduced the average soluble sugar,starch and NSC concentration of Q.acutissima seedlings,and changed the distribution of NSC in different organs.The concentration of soluble sugar and NSC in leaves increased significantly,while the concentration of soluble sugar and NSC in stems and roots decreased.Ectomycorrhiza reduced the content of average NSC in Q.acutissima seedlings under drought and high calcium treatments,but increased the concentration of soluble sugar in roots.While the concentration of soluble sugar and NSC in roots of inoculated seedlings under high-calcium-drought treatments were increased significantly.(3)At the early stage of treatment,compared with the drought treatment,high calcium and high-calcium-drought treatments significantly reduced the net photosynthetic rate of Q.acutissima seedlings.After three months of treatment,drought,high calcium and high-calcium-drought treatments significantly inhibited net photosynthetic rate.And inoculated with ectomycorrhiza significantly increased net photosynthetic rate.Under drought treatment,the soluble protein content in leaves of Q.acutissima seedlings were decreased,the activities of SOD,APX,DHAR,GR and GST were increased,while the activities of SOD,POD,APX and DHAR were increased significantly in high calcium and high-calcium-drought treatments.Ectomycorrhiza increased soluble protein concentration and decreased MDA concentration in leaves of Q.acutissima seedlings under drought,high calcium and high-calcium-drought treatments.(4)In normal calcium environment,ectomycorrhiza could activate soil calcium,promote plant calcium uptake,improve plant water use efficiency,and increase plant drought resistance.Drought significantly reduced the concentration of water-soluble calcium in soil,while inoculation with ectomycorrhizal fungi significantly increased the concentration of water-soluble calcium and exchangeable calcium in soil,and the calcium concentration in leaves,stems and roots of inoculated seedlings were increased compared with those of non-inoculated seedlings.At the same time,inoculation with ectomycorrhizal fungi significantly increased water use efficiency of Q.acutissima seedlings,and calcium content of leaves,stems and whole plants under drought treatment were positively correlated with water use efficiency.(5)Under high calcium and high-calcium-drought treatments,ectomycorrhiza could significantly reduce root calcium concentration and calcium content,but under high-calcium-drought treatment,ectomycorrhiza increased leaf calcium concentration and content.At the same time,ectomycorrhiza could increase the uptake of nitrogen and phosphorus in various organs of Q.acutissima,which is an important reason why ectomycorrhizal can improve the growth of Q.acutissima in adversity.The high-calcium environment had a negative effect on the net photosynthetic rate of Q.acutissima seedlings,and the concentration and distribution of NSC were different from that of drought treatment.At the same time,high calcium and drought had synergistic effects on inhibition plant.Ectomycorrhiza could improve the photosynthetic process and stress-resistant enzyme activity of Q.acutissima,seedlings,and help plants adapt to high calcium and drought environment. |
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