Study On The Response Of Mycorrhizal Pinus Koraiensis Seedlings To Drought Stress

Drought stress is an important environmental factor affecting plant growth.When afforestation and urban landscape greening are carried out,plants are subjected to drought stress,which leads to their own dysfunction or even decline.Ectomycorrhizal fungi(ECMF)can form ectomycorrhiza(ECM)with plant roots.When plant roots form symbiotic ectomycorrhiza,the ability of roots to absorb soil nutrients and drought tolerance are enhanced.Pinus koraiensis is a typical ectomycorrhizal dependent tree species.The symbiotic mycorrhiza formed by its roots and ectomycorrhizal fungi can promote the healthy growth of Pinus Koraiensis in adverse environments.In this study,three kinds of ECMF [ Boletus edulis Bull.: Fr.(M1),Cortinarius collinitus(Pers.)Fr.(M2),Suillus grevillei(Kl.)Sing.(M3)] were selected.Firstly,PEG-6000 was used to simulate seven drought levels to test the drought tolerance of three kinds of ECMF.The mycelial growth diameter,mycelial biomass,cellulase,urease and catalase activities under different drought stresses were detected to determine the drought tolerance of the three ECMFs.Then,the indoor pot method was used to conduct drought stress experiments on three kinds of Pinus koraiensis mycorrhizal seedlings and uninoculated Pinus koraiensis seedlings by setting normal and three levels of drought treatment.By measuring the changes of main growth indexes,physiological indexes,soil physical and chemical indexes and soil enzyme activities of Pinus koraiensis ectomycorrhizal seedlings under drought stress,the drought tolerance of Pinus koraiensis mycorrhizal seedlings under drought stress was analyzed.Whether there are significant differences in enhancing the drought tolerance of Pinus koraiensis seedlings by three kinds of ECMF,and the effects of ECMF on soil indexes and soil enzyme activities,the results are as follows :(1)Effects of PEG drought stress on the growth of three ECMFs.In the PEG simulated drought stress experiment,the ectomycorrhizal fungus M1 had the smallest inhibition rate,the largest growth rate and biomass in severe drought treatment.The cellulase and laccase activities of the three ECMFs decreased with the increase of PEG drought stress,and the above indexes of M1 decreased the least.The peroxidase activity of the three mycorrhizal fungi reached the highest under 20 % PEG drought conditions.The order of peroxidase activity of mycorrhizal fungi was M1 > M2 > M3.The above experimental results showed that M1 showed strong drought tolerance under PEG drought stress.(2)Effects of drought stress on growth and physiological indexes of Pinus Koraiensis mycorrhizal seedlingsFirstly,three ECMFs could form symbiotic mycorrhiza with P.koraiensis seedlings,and the mycorrhizal infection rate was M3 > M2 > M1 > CK,and the mycorrhizal infection rate was significantly positively correlated with seedling height,ground diameter,fresh weight and dry weight.Compared with uninoculated seedlings,ECMF inoculation significantly increased the plant height and total biomass of seedlings.The above results showed that inoculation of ectomycorrhizal fungi could promote the growth of Pinus koraiensis seedlings.Comparing the physiological indexes of inoculated and uninoculated Korean pine seedlings under drought stress,it was found that the MDA content of mycorrhizal seedlings was significantly lower than that of uninoculated Korean pine seedlings,and the MDA content of mycorrhizal seedlings inoculated with M3 was the lowest.With the increase of drought stress,the content of soluble sugar and soluble protein in plant leaves showed a trend of decreasing first and then increasing,and there was a significant difference with the control treatment.The activities of Pro,POD and SOD of three ECM seedlings increased with the increase of drought stress,and were significantly higher than those of uninoculated seedlings.The mycorrhizal infection rate of Pinus koraiensis seedlings under drought stress was positively correlated with seedling dry weight,SOD and Pro,and negatively correlated with MDA.The above indexes of mycorrhizal seedlings inoculated with M3 were better than those of other strains.The above results showed that ECMF could resist the negative effects of drought stress on Pinus koraiensis seedlings to varying degrees,and the mycorrhizal seedlings inoculated with M3 showed strong drought tolerance.(3)Effects of drought stress on rhizosphere soil indexes and soil enzyme activities of Pinus koraiensis mycorrhizal seedlingsUnder normal water and drought stress conditions,the contents of soil organic matter,total nitrogen,total phosphorus and alkali-hydrolyzable nitrogen in the inoculated seedlings were significantly higher than those in the uninoculated seedlings.The activities of urease,acid phosphatase,alkaline phosphatase and catalase in soil inoculated with M3 were higher than those of other strains.The results of correlation analysis showed that the mycorrhizal infection rate of Pinus koraiensis seedlings was significantly positively correlated with root activity,soil organic matter and total phosphorus content under drought stress.It was significantly positively correlated with total nitrogen and alkaline nitrogen content and urease activity.There was no significant correlation with available phosphorus content,alkaline phosphatase,acid phosphatase and catalase.Root activity was significantly positively correlated with alkaline phosphatase and urease,and significantly positively correlated with alkaline nitrogen.In summary,the drought tolerance of different ECMFs was different.The mycorrhizal seedlings of Pinus koraiensis formed by different strains also showed different drought tolerance under drought stress,and were more resistant to drought than uninoculated seedlings.Because M1 mycorrhizal fungi showed better drought tolerance under PEG simulated drought stress,and Pinus koraiensis mycorrhizal seedlings inoculated with M3 showed stronger drought tolerance under drought stress.Therefore,in the process of evaluating the preferred strains of mycorrhizal fungi to improve plant drought tolerance,it is not only necessary to rely on the drought tolerance of mycorrhizal fungi themselves,but also to comprehensively evaluate the growth performance of mycorrhizal plants under drought stress after ECMF inoculation.