Effects Of Arbuscular Mycorrhiza On Nitrogen Utilization And Root Physiology Of Flue-Cured Tobacco

80% of terrestrial plants can form symbionts with arbuscular mycorrhizal fungi,improve plant root structure,and promote the absorption of nutrient elements by plant roots.In this study,AMF fungi were inoculated under different nitrogen application rates to explore AMF under different nitrogen application rates.The effect of fungi and flue-cured tobacco symbiosis on root morphology,physiology and nitrogen utilization of flue-cured tobacco.The main conclusions of this study are as follows:1)There was no significant relationship between the infection of flue-cured tobacco roots by AMF fungus infecting flue-cured tobacco and the nitrogen application rate.Nitrogen application can promote the growth of flue-cured tobacco roots,and has a significant effect on root length,volume and surface area,but the diameter,root tip number,specific root length and specific surface area of flue-cured tobacco roots did not increase with the increase of nitrogen application;root activity was the strongest under high nitrogen application(1.25 g/plant).Inoculation of AMF fungi has little effect on root diameter,root tip number,specific root length,and specific surface area;when the nitrogen application rate is 0.5-0.75g/plant,inoculation of AMF fungi is beneficial to the growth of flue-cured tobacco roots,and promotes root length and surface area,and increase in size.2)Nitrogen fertilizer application can enhance the nitrate reductase activity in flue-cured tobacco leaves and the urease activity in tobacco-growing soil,but the nitrate reductase activity under high nitrogen application rate is lower than that under low nitrogen treatment,and the nitrogen application rate is 1.25g/g/g.The soil urease activity was the strongest at the time of planting.When the nitrogen application rate was 0.5-0.75g/plant,the soil urease content increased after inoculation with AMF fungi.3)Within the range of suitable nitrogen application rate,increasing the nitrogen application amount of topdressing fertilizer was beneficial to the growth and development of tobacco plants and the accumulation of dry matter.The biomass of flue-cured tobacco showed an increasing trend with the increase of nitrogen fertilizer application;In the low nitrogen treatment,the inoculation of AMF had a certain effect on the agronomic characters and biomass of flue-cured tobacco,but it had little effect under the high nitrogen application.When the nitrogen application rate was high(1.00-1.25 g/plant),the contents of various chemical components in tobacco leaves were higher,while the nitrogen application rate had little effect on the chloride ion content of flue-cured tobacco leaves;After inoculation with AMF fungus,the content of total nitrogen,total sugar and reducing sugar in tobacco leaves was reduced,and the content of potassium ion and nicotine was increased.The effect of internal total phosphorus content was not obvious;AMF fungi had little effect on chloride ion content.4)Nitrate nitrogen content,ammonium nitrogen content in flue-cured tobacco leaves,nitrogen accumulation in tobacco leaves,nitrogen absorption efficiency of flue-cured tobacco shoots and nitrogen absorption from fertilizer increased with the increase of nitrogen application rate.When the nitrogen application rate was0.5-0.75g/plant,the nitrogen absorption efficiency of the above-ground parts of flue-cured tobacco and the amount of nitrogen absorbed by flue-cured tobacco from fertilizers increased.Nitrate nitrogen and ammonium nitrogen contents in flue-cured tobacco leaves showed an upward trend after inoculation with AMF fungus,but had no significant effect on the accumulation of nitrogen in the shoots of flue-cured tobacco.Under the low nitrogen application rate,the inoculation of AMF fungi increased the nitrogen absorption efficiency of flue-cured tobacco shoots and the amount of nitrogen absorbed by the flue-cured tobacco from the fertilizer,but had no significant effect at the high nitrogen application rate;When the nitrogen application rate was 0.5-0.75g/plant,the nitrogen absorption efficiency of the shoots of flue-cured tobacco and the amount of nitrogen absorbed by the flue-cured tobacco from the fertilizer increased after inoculation with AMF fungi.The effect of nitrogen application rate and AMF fungus on nitrogen utilization efficiency of flue-cured tobacco was not obvious.