Effects Of Arbuscular Mycorrhizal Fungi On Growth And Drought Resistance Of Vitex Negundo Seedlings

Arbuscular mycorrhizal fungi(AMF)have strong adaptability and can combine with many kinds of plants.AMF plays an important role in improving the function of terrestrial ecosystem by infecting plants to form mutually beneficial symbiosis.Under the influence of mycorrhizal-plant symbiosis,the tolerance and resistance of host plants to stress increased significantly.Drought is one of the main problems facing urban ecological development in China.Drought makes it difficult for plants to absorb water from roots,water deficit in plants,slow growth and yield reduction,leading to plant growth regression and facing adversity stress.It was found that inoculation of mycorrhizal fungi could improve the adverse effects of drought on plants.In this study,mycorrhizal fungi were inoculated on common vegetation of Vitex negundo in Taihang Mountains.The effects of AMF inoculation on the growth and drought resistance of Vitex negundo were investigated by simulating different drought conditions.It provides an important theoretical basis for the study of physiological mechanism of drought resistance of Vitex negundo and a technical reference for ecological restoration in Taihang Mountains.It lays a foundation for the application of AMF in vegetation restoration in arid and semi-arid areas.The main conclusions are as follows:(1)Water stress reduced AMF mycorrhizal infection rate and biomass of Vitex negundo,and increased its mycorrhizal dependence.AMF inoculation significantly increased the biomass of Vitex negundo.Under three water treatments,the dry weight of above-ground and underground parts of Vitex negundo increased significantly.AMF inoculation significantly increased plant height,basal diameter and leaf area of Vitex negundo.The plant height and leaf area of Vitex negundo decreased with the decrease of soil moisture content,and the basal diameter increased first and then decreased.Water stress and inoculation had significant interaction effects on biomass and mycorrhizal infection rate of Vitex negundo(P < 0.05),but had no significant interaction effects on plant height,basal diameter and leaf area(P >0.05).(2)Under three water conditions,inoculation with AMF significantly increased root length,root surface area,root volume and root tip number,and decreased root mean diameter.With the decrease of soil moisture content,root length and volume of Vitex negundo decreased gradually,root surface area and root tip number increased first and then decreased,and root average diameter increased gradually.Water stress and inoculation had no significant interaction effect on root length,root volume and root mean diameter(P > 0.05),but had significant interaction effect on root surface area and root tip number(P <0.05).(3)Under three water conditions,inoculation with AMF significantly reduced MDA content in leaves of Vitex negundo and alleviated the damage of drought to plants.With the decrease of soil moisturecontent,MDA content in leaves of Vitex negundo increased significantly.The activities of SOD,POD and CAT were significantly increased by AMF inoculation.With the increase of drought stress,SOD content in leaves of Vitex negundo increased first and then decreased,POD and CAT content gradually increased,and antioxidant enzyme system was continuously upgraded.Water stress and inoculation had no significant interaction effect on MDA content and SOD content(P > 0.05),but had significant interaction effect on POD and CAT content(P < 0.05).(4)Under three water conditions,inoculation with AMF significantly increased net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)and decreased intercellular CO2concentration(Ci)in leaves of Vitex negundo.With the decrease of soil moisture content,the net photosynthetic rate and other indicators of Vitex negundo leaves decreased significantly,and the intercellular CO2 concentration of Vitex negundo leaves showed an upward trend.Water stress and inoculation had no significant interaction effects on net photosynthetic rate,stomatal conductance,transpiration rate and intercellular CO2 concentration(P > 0.05).(5)Under three water conditions,AMF inoculation significantly increased the primary light energy conversion efficiency(Fv/Fm)and the potential photochemical activity(Fv/F0)of PSI in the leaves of Vitex negundo.The drought resistance of Vitex negundo seedlings under water stress was improved.The light use efficiency of Vitex negundo decreases with the decrease of soil moisture content.There was no significant interaction between inoculation and water treatment on Fv/Fm and Fv/F0 of Vitex negundo(P >0.05).