| We selected 1-year and 2-year-old Pinus sylvestris var.mongolica.We measured the growth index,nutrient content,root morphological structure of Pinus sylvestris seeding with and without the inoculation of ectomycorrhizal fungi in different nitrogen concentration treatments,including no nitrogen(0N),1-fold nitrogen concentration(CN),2-fold nitrogen concentration(2CN)and 3-fold nitrogen concentration(3CN).We were analyzed different nitrogen concentration treatments and mycorrhizal fungi inoculation on Pinus sylvestris var.mongolica seedlings.The purpose of understand the response of mycorrhizal symbiosis in nitrogen deposition in nature.The results are as follows:1.The results of 1-year-old potted seedlings:(1)Under different nitrogen concentrations,inoculation significantly increased the mycorrhizal infection rate,seedling height,ground diameter,aboveground biomass,underground biomass and N,P nutrient content of seedlings.(2)With the increase of nitrogen concentration,the aboveground biomass of mycorrhizal and non-mycorrhizal seedlings increased tendency;the increase of nitrogen concentration had no significant effect on the underground biomass of non-mycorrhizal seedlings,but significantly increased the underground biomass of 2CN treated seedlings.(3)With the increase of nitrogen concentration,the specific root length and specific root surface area of mycorrhizal and non-mycorrhizal seedlings increased significantly,and the root tissue density were maximum in CN treatment;At the same time,there was no significant effect on the total branching number of non-mycorrhizal seedlings,but the total branching number was decreased significantly in 2CN treatment mycorrhizal seedlings..(4)In different N concentration treatments,The nutrient content of N and P in non-mycorrhizal seedlings was CN>2CN>0N,while that in mycorrhizal seedlings was 2CN>CN>0N.2.The results of 2-year-old nursery seedling:(1)With the increase of nitrogen concentration,the infection rate of mycorrhiza in the inoculated and non inoculated treatments were decrease significantly,and the infection rate was no significant of inoculated and non inoculated treatments in 3CN;The infection rate of mycorrhiza in the inoculated treatment was significantly higher than the non inoculated treatment in nitrogen concentration of(0N,CN,2CN),(2)With the increase of nitrogen concentration,the aboveground and underground biomass of seedlings were increased first and then decreased tendency in different inoculation treatments;the aboveground and underground biomass of seedlings with inoculation and non inoculation treatment were the maximum in 2CN treatment.(3)With the increase of root grade,the effects of nitrogen addition and inoculation treatment in root morphology decreased.The inoculated and non inoculated seedlings in 2CN treatment was higher than other nitrogen concentrations treatment that the specific root length and specific root surface area of the first-order roots of the seedlings.(4)With the increase of nitrogen concentration,the content of N and P increased first and then decreased with mycorrhizal and non-mycorrhizal seedlings of the above ground part.The content of N and P of the underground part of non-mycorrhizal seedlings in CN and 2CN treatment were maximum,and the content of N in the underground part of mycorrhizal seedlings in the treatment of CN,2CN and 3 CN were significantly higher than that under the treatment of 0N.(5)With the increase of nitrogen concentration,The no inoculation seedlings was significantly decreased in roots,stems and leaves of the content the soluble sugar,and the effect of nitrogen addition was weak of the content of soluble sugar.Nitrogen addition significantly increased starch content of seedlings in all organs.To sum up,low nitrogen treatment can promote the growth of seedlings,the formation of root morphology,and the increase of nutrient carrying capacity.The inoculation treatment can improve the tolerance of seedlings when nitrogen input. |
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