Effects Of Arbuscular Mycorrhizal Fungi Inoculation On Growth And Drought Resistance Of Prunus Salicina Under Drought Stress

Due to the high nutrition and economic value,Prunus salicina has developed rapidly in recent years and gradually become one of the important commercial crops.Prunus salicina are widely cultivated in China and all over the world.Southern region is recognized as optimal production areas in our country,but much of the south has a high incidence of seasonal drought.Not only is it intense,but also lasts for a long time,the evaporation loss of water vapor is large during the hot weather,so the heat and drought tend to occur at the same time.Prunus salicina are mostly cultivated in hilly areas,where the soil is poor and difficult to store water,making them more vulnerable to drought stress.These factors have seriously affected the normal physiological metabolism and product quality of Prunus salicina and restricted the development of local economy.Arbuscular mycorrhizal fungi（AMF）can form mutually dependent mutualistic symbiosis with the roots of Prunus salicina,which can improve the resistance of the plant to drought.In this study,―Wushancuili‖was used as material,the good growth and healthy seedlings of Prunus salicina was selected.The arbuscular mycorrhizal fungi of Claroideoglomus etunicatum was denoted as（Ce）and Funneiiformis mosseae was denoted as（Fm）.Two kinds of drought gradients were set by means of artificial water control:normal water supply,denoted as（WW）;drought stress,denoted as（DS）.In order to study the effects of two kinds of AMF on leaves and roots growth and photosynthesis of Prunus salicina under long-term drought stress,regulation of antioxidase activity,osmoregulatory substances,endogenous hormones and influence on gene expression of key enzymes in ABA synthesis.Comprehensive analysis the effects of AMF on the growth and drought resistance of Prunus salicina seedlings under drought stress.The results are as follows:1.Regardless of drought stress or normal water supply,C.e and F.m can infect seedlings roots in varying degrees and form a good arbuscular mycorrhizal structure.Under drought stress,Prunus salicina seedlings were more dependent on arbuscular mycorrhiza.The infection rates of C.e and F.m also reached 41.90%and 44.89%,the infection rates under normal water supply exceeded 50%.In terms of impact,F.m is better than C.e on the whole.Compared with uninoculated plants,mycorrhizal symbiosis can increase the plant height,chlorophyll,carotenoid content and photosynthesis ability,promote plant growth and development,but the stem thickness did not change significantly.Two kinds of AMF can also promote the roots growth,increase roots vigor,root-shoot ratio and root volume,increase the number of first-level new root and longest lateral root,expand root absorption area,provide excellent conditions for plants to absorb water and mineral nutrition.2.Under drought stress,Two kinds of AMF had promoted the accumulation of soluble sugar,soluble protein and proline in the leaves and roots,increased the activity of superoxide dismutase（SOD）,catalase（CAT）and peroxidase（POD）,reduced the content of hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）.As the drought time increased,the drop rate of H₂O₂ and MDA is greater.On the one hand,both AMF maintained normal osmotic potential and cell integrity through osmotic regulation;On the other hand,it can improve the activity of antioxidant enzymes,remove excessive reactive oxygen,prevent cell membrane lipodization,reduce oxidative damage.They worked together to enhance the drought resistance of host plants.3.Drought stress promoted the endogenous hormone content to decrease in plants,the decreasing trend was delayed to a large extent after AMF inoculation.The contents of abscisic acid（ABA）,auxin（IAA）,gibberellin（GA3）and zeatin riboside（ZR）in leaves and roots of mycorrhized seedlings were significantly higher than those of unmycorrhized seedlings.Under drought stress,AMF enhanced the positive regulation of plant growth and development by regulating the balance of endogenous hormones.Abscisic acid（ABA）was regarded as an important stress hormone.The inoculating plants can increase the content of ABA to enhance the drought tolerance of plants.4.PSNCED3 is a key enzyme gene in ABA synthesis,ABA accumulation is based on the regulation of PSNCED3.Ps Sn RK2.2 is an unique protein kinase in plants,which plays a inportant role in plant resistance to stress.Ps Sn RK2.2 can be activated by ABA to induce the expression of related resistance genes.AMF could up-regulate the expression levels of PSNCED3 and Ps Sn RK2.2 genes,the effect in roots was better than that in leaves,which effectively enhanced the drought resistance ability of Prunus salicina seedlings.