| Arbuscular Mycorrhizal Fungi(AMF)can form symbiosis with many species of plants,which can enhance the utilization of soil nutrients by fungi.As an important nutrient harvesting organ of plants,roots usually make a series of morphological and physiological changes in the heterogeneous environment of nutrients,showing different growth strategies,which affect the foraging behavior of roots.Nitrogen is the main nutrient element for plant growth.Soil nitrogen and AMF can affect the morphology and physiological condition of fine roots.In this study,Vitex negundo was used as the experimental material.Two groups of experiments were set up: no AMF(N group)and AMF(AN group).Four nitrogen application levels were set in each group and each pot(N content was 0 mg·kg-1,90 mg·kg-1,175 mg·kg-1,350mg·kg-1,respectively).The inoculated group(AN)had 10 g Fungal content,and the control group(CK).The effects of soil nitrogen nutrient on root physiology and morphology of Vitex negundo root under AMF inoculation were studied.The main research results are as follows:(1)Nitrogen addition and inoculation of Arbuscular Mycorrhizal Fungi could promote the aboveground indices and root biomass of Vitex negundo.The AN treatment is significantly better than the N treatment.Compared with other groups,the leaf number,leaf area and root biomass of AN group were significantly increased,and mycorrhizal symbiosis significantly improved the nutritional status of Vitex negundo.(2)The rate of mycorrhizal infection and the density of spores in rhizosphere soil were increased by nitrogen addition.The increase of mycorrhizal infection rate at low nitrogen(90 mg·kg-1)and medium nitrogen(175 mg·kg-1)concentrations was significantly higher than that at high nitrogen(350 mg·kg-1)concentrations.High nitrogen concentration was not conducive to spore germination and mycelium growth,and reduced the effective infection capacity of AMF.(3)The morphological indexes of fine roots(root length,surface area,root volume,root biomass,root tissue density,etc.)were better under inoculation(AN)than without inoculation(N).Inoculation with AMF increased fine root length,root surface area,root volume and root biomass,while decreased fine root tissue density.At low nitrogen concentration(90 mg·kg-1),the root growth was more dominant,while at high nitrogen concentration(350 mg·kg-1),the root growth was poor,reflecting that the root growth was limited and the mycorrhizal effect was weakened at high concentration.(4)The physiological indexes of fine root(nutrient content,root activity,SOD activity,POD activity and CAT enzyme activity,soluble protein content,etc.)of inoculated(AN)were better than those of non-inoculated(N),and the MDA content of fine root of inoculated(AN)was lower than that of non-inoculated(N).AMF inoculation increased nitrogen content,carbon content,phosphorus content,root activity,SOD activity,POD enzyme activity,CAT enzyme activity and soluble protein content in fine roots of Vitex negundo,and decreased MDA content in fine roots.Mycorrhizal symbiosis promoted nutrient absorption and root antioxidant enzyme system operation,and maintained root vitality.The contents of nitrogen,carbon,POD activity,SOD activity and CAT activity in the fine root of Vitex negundo were the highest in the low nitrogen(90 mg·kg-1)concentration.The content of MDA was minimum at low nitrogen(90 mg·kg-1)concentration.The effect of low nitrogen(90mg·kg-1)on root activity and soluble protein was more obvious.(5)The biomass of fine roots was positively correlated with nitrogen content,carbon content,POD,SOD activity and soluble protein content.The surface area of fine roots was positively correlated with soluble protein content and negatively correlated with MDA content.There was a significant negative correlation between fine root length and MDA content. |
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