| Soil saline-alkali seriously affects the growth of plants.As the dominant species in songnen grassland,Leymus chinensis has developed roots,drought resistance,saline-alkali resistance,and strong asexual reproduction and regeneration ability.Three kinds of shrubs,such as Nitraria tangutorum,Elaeagnus angustifolia and Lycium barbarum,can also adapt to degraded soil and have strong saline-alkali resistance,which are better protective plants for greening along saline-alkali soil.In addition,The arbuscular mycorrhizal fungus can form symbiosis with these four kinds of plants and improve the saline-alkali tolerance of plants.Therefore,the use of AM fungi to promote the growth of plants in saline-alkali land can not only reveal the intrinsic mechanism of AM fungi to improve the saline-alkali tolerance of leymus chinensis and three kinds of shrubs,but also provide certain scientific guidance for production practice.In this study,Leymus chinensis,Nitraria tangutorum,Elaeagnus angustifolia and Lycium barbarum were taken as the research object,and the effects of AM fungi on the growth and physiology of host plants under different saline-alkali stresses were investigated through pot control experiments in two growing seasons,and the indirect effects of phosphorus application on AM fungi on the improvement of Leymus chinensis.At the same time,field treatment experiments were carried out on Leymus chinensis population in two growing seasons to explore the quantitative characteristics and ecological plasticity under the action of AM fungus inoculation.The main conclusions are as follows:(1)Saline-alkali stress significantly inhibited the root colonization rate and infection intensity of AM fungi on Leymus chinensis,Nitraria tangutorum,Elaeagnus angustifolia and Lycium barbarum.The affinity between different AM fungi and Leymus chinensis was different.Under low Saline-alkali stress S1(50 mM),the colonization rate and infection intensity of Leymus chinensis root inoculated with Septoglomus constrictum(Sc)were the highest,with values of 79.00%and 57.75%,respectively,and the colonization rate and infection intensity of Leymus chinensis root inoculated with Funneliformis geosporum(Fg)were the lowest,with values of 70.20%and 47.51%,respectively.Under high saline-alkali stress S3(200 mM),the highest colonization rate and infection intensity of Leymus chinensis root under mixed inoculation(M)were 64.00%and 43.75%,respectively,while the lowest values of Fg were 54.70%and 41.47%,respectively.Similarly,phosphorus levels of AM fungi infection Leymus chinensis root also had an impact,no stress,various of AM fungi of Leymus chinensis mycorrhizal mycorrhizal colonization rate and infection intensity of infection difference is small,have Saline-alkali stress,phosphorus level P2 and P3(50 mg P/kg and 100 mg P/kg),inoculated with Funneliformis mosseae(Fm)of Leymus chinensis root colonization rate is highest,its value were 76.50%and 72.50%respectively,P4 high phosphorus level(150 mg P/kg)Leymus chinensis inoculation M under root infect the highest colonization rate and infection intensity,70.15%and 40.23%,respectively.(2)AM fungi can promote the biomass growth of host plants under saline-alkali stress.Different AM fungi had different promoting effects on the biomass growth of Leymus chinensis.Among them,Fm,Sc and M inoculation could significantly increase the aboveground biomass of Leymus chinensis,1.26,1.27 and 1.31 times of the control group in S1 treatment,1.44,1.35 and 1.39 times of the control group in S2(100 mM)treatment,1.44,1.35 and 1.39 times of the control group in S2 treatment,and 1.36,1.29 and 1.36 times of the control group in S3 treatment.When Fm and Sc were inoculated without saline-alkali S0(0 mM),the belowground biomass was 1.40 and 1.37 times of that of the control group,and 1.65 and 1.68 times of that of the control group,respectively.Under saline-alkali stress and P additiong,have saline-alkali stress and lower level of phosphorus P1(25 mg P/kg),inoculated Fm and M significantly improves the below ground biomass of Leymus chinensis,and Fm 1.38 times and 1.82 times of the control group,M 1.41 times and 1.62 times of the control group.under high phosphorus level P4,in addition to the Sc,the other AM fungi and host plants from mutual symbiosis become a parasitic relationship.(3)Saline-alkali stress makes four host plants suffer from Na+ and Cl-toxicity,and AM fungus inoculation can reduce the Na+ and Cl-content of host plants,and also improve the absorption of K+,so as to improve the saline-alkali tolerance of plants.However,at high phosphorus level,the Na+and Cl-contents in plants were no longer decreased after AM fungus inoculation in the absence of saline-alkali stress.(4)AM fungus inoculation can promote the absorption of N and P elements by four host plants,and improving the saline-alkali tolerance of plants.However,at high phosphorus levels,AM fungus inoculation no longer promoted the absorption of N and P by host plants.AM fungi can improve the saline-alkali tolerance of host plants by enhancing the activity of antioxidant enzymes in host plants and improving the osmotic regulation of host plants.AM fungi improve saline-alkali tolerance of host plants in enhance the antioxidant enzyme activity of host plants,and improve the osmotic regulation ability of the Leymus chinensis inoculation of AM fungi,Nitraria tangutorum,Elaeagnus angustifolia and Lycium barbarum no inoculation of AM fungi,its SOD,POD and CAT enzyme activity were increased,MDA content decreased,and soluble sugar,soluble protein and proline content were increased.(5)The populations of Leymus chinensis inoculated with AM fungi showed significant improvement in various quantitative characteristics.The inflorescence biomass and total biomass of Leymus chinensis populations inoculated with AM fungi grew as a power function,but there was no obvious correlation between the inflorescence biomass and total organisms of Leymus chinensis populations not inoculated with AM fungi.There is a significant negative correlation between the total biomass,and the law of allometric decline of power function is followed,which not only reflects the greater ecological plasticity and stronger adjustability between the populations,but also reflects the presence of Leymus chinensis populations.A similar growth regulation strategy is exhibited for the harsh living environment,that is,by sacrificing the reproductive growth of Leymus chinensis,priority is given to ensuring vegetative growth. |
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