Effects Of AM Fungi On The Growth And Nutrient Utilization Of Cirtnamomum Bodinieri Seedlings Under Increasing CO₂ Concentration

Arbuscular mycorrhizal fungi（AMF）is an important soil microorganism that is widely distributed in terrestrial ecosystems and forms symbiosis with the roots of most higher plants.Arbuscular mycorrhizal（AM）is the symbionts of plants and arbuscular mycorrhizal fungi.This symbionts can obtain the necessary carbohydrate and other nutrients from plants.Meanwhile the fungal hyphae absorbs nutrients and water from the soil and transfers them to the plant for growth,which can achieve the purpose of mutual benefit and mutual assistance in the end.They are characteristics of complex structure,high habitat heterogeneity and vulnerability in Karst ecosystem.with the global climate changing,a sharp rise in CO₂ concentration leads that the adaptability and species diversity of plants are facing more new challenges in karst areas.Mycorrhizal technology can overcome some problems of fragile habitat in karst areas.Studies have showed that elevated atmospheric CO₂ had important effects on the habitat and physiological ecology of plants.However,these studies only considered the effects of elevated atmospheric CO₂ on plant growth,morphological structure and physiological function.Studies in which mycorrhizal fungi,including AM fungi affects plant growth and soil nutrient is still relatively weak.In addition,previous studies did not involve that the adjacent individual plants through AM mycelium interaction in response to elevated atmospheric CO₂ in karst.Therefore,this research used the karst optimum plant of Cirtnamomum bodinieri as the research object,and through the supply of high concentration CO₂ to simulate the elevated atmospheric CO₂ plant growth environment.Explores how CO₂ supply influences plant growth and nutrient utilization under the presence of AM fungi.This plays an important role in illuminating the habitat adaptability of plants,and the function relationship between soil microorganisms and plant in karst areas.This experiment device is a conjoined compartment composed of the donor compartment of carbon dioxide（D compartment）and the receiver compartment of carbon dioxide（R compartment）.Mycelium isolation technology was used to construct high CO₂ concentration factor,AM fungal inoculation factor and nylon mesh factor for indoor control experiment.Cirtnamomum bodinieri seedlings were planted in both of the D compartment and the R compartment.D compartments were treated with CO₂ treatment（C⁺）or non CO₂ treatment（C^-）,and the corresponding R compartment was the corresponding C+treatment and C-treatment.Both D and R compartments were treated with AM fungi（M⁺）or not（M^-）.The middle plates of D compartment and R compartment were treated with 20μm nylon mesh and 0.45μm nylon mesh respectively.（20μm nylon mesh is that AM mycelium can pass through the mesh but the plant root cannot;0.45μm nylon mesh is that AM mycelium and plant root cannot pass through the mesh）.The phenotypic characters,and plant nutrients of Cirtnamomum bodinieri,and soil characters were measured.The main results are as follows:（1）In terms of growth characteristics,AM fungi significantly increased the seedling height,ground diameter and leaf area,and the root,stem,leaf and total biomass of seedlings with high CO₂concentration treatment.At the same time,AM fungi influenced the length,surface area,volume,average diameter,tip number and bifurcation number of root differently.High CO₂ concentration mainly significantly improved the seedling height,ground diameter,leaf area and root character indexes of AM fungal inoculated seedlings in D compartment.The effect on the seedlings in R compartment was mainly reflected in surface area,volume,and bifurcation number of root under the condition of mycelium can pass through the nylon mesh.（2）In terms of nutrients of plants,the inoculation of AM fungi can significantly increase the nitrogen and phosphorus concentration of seedlings and potassium under the condition of high CO₂ concentration.AM fungi significantly increased the carbon accumulation of plant in the donor compartment of carbon dioxide and the root and stem carbon accumulation in the receiver compartment of carbon dioxide.Besides,AM fungi significantly promoted the nitrogen,phosphorus and potassium acquisition of seedlings.High CO₂ concentration can significantly improve the nitrogen and phosphorus concentration and carbon accumulation of plants inoculated AM,and significantly affected the root and stem potassium concentration under the condition of mycelia could pass through the mesh.High CO₂ concentration mainly significantly increased the nitrogen,root and stem phosphorus acquisition of the donor compartment of carbon dioxide,and the leaf and total nitrogen and phosphorus acquisition of the receiver compartment of carbon dioxide under the condition of mycelia could pass through the mesh.（3）For soil nutrients,the effects of AM fungi on soil nutrients were relatively significant under the treatment of high CO₂ concentration.AM fungi significantly increased the contents of soil organic carbon and soil GRSP,while reduced the contents of nitrogen,phosphorus and potassium in soil of the donor compartment of carbon dioxide.At the same time,AM fungi decreased the nitrogen and potassium content,while increased organic carbon in the soil of the receiver compartment of carbon dioxide.High CO₂ concentration significantly decreased the nitrogen,phosphorus and available potassium,while increased the organic carbon content in soil under the condition of mycelium passing through the mesh.（4）As a conclusion,high CO₂ concentration and AM had different effects on the phenotypic traits,and nutrients acquisition,and soil nutrients of Cirtnamomum bodinieri seedlings respectively.The connective hyphae between two compartments promoted the growth and nutrient utilization of neighboring plants.The effects of AM fungi on plant and soil nutrients were more significant with high CO₂ concentration supply.Elevated CO₂ significantly promoted the growth and nutrient uptake of plants in the donor compartment of carbon dioxide.While the effect on seedlings of the receiver compartment of carbon dioxide was less significant than that of the donor compartment of carbon dioxide.High CO₂ concentration and AM fungi may have a synergistic effects on the growth,and nutrient utilization of Cirtnamomum bodinieri seedlings.