Effects Of The Different Arbuscular Mycorrhizal Fungi On The Growth And Al Tolerance Of Pear Seedlings Under The Stress Of Aluminium

Aluminum is the most abundant metal element in the earth’s crust.a large number of Al is riched with the course of red soil’s development.Statistical data shows that acidic reaction strongly in soil brings out the enrichment of Al and the low availability of soil nutrients.In recent years,along with the worsening of global environment, many areas have appeared the harm of acid rain.The frequent acid rain, which speeds up the soil acidification and simultaneously activates lots of aluminum in the soil, severely restricts the growth of plants.With the extension of planting years, acidification trend of the soil has became increasingly apparent in orchards. Acidification problem of the soil has became one of the most important limiting factors for the sustainable development of orchard production at present.The soil shows more acidity in the South Mountain Orchards. Because they mostly distribute at the nearby of somewhere which have convenient traffic condition and highly developed industries.Impacting of the acid rain is inevitable. For example, Chongqing gold orchard’s soil shows strong acidity with pH at 4.55 or less, The fruit trees are contaminated easily due to a large number of active aluminum.Along with the growing population and decreasing plough,it is very important to govern and develop the Al-rich soil.Pear is one of the largest traditional fruits in China.The planting area of pear is widely distributed.This research is about two aspects,one is that how can the Arbuscular mycorrhizal fungi(AMF) effects the aluminum tolerance of the pear, another is that what physiological mechanism happened during the process.The research result is helpful to improve the yield and quality of pear, it’s also helpful to improve the application of the Al-rich soil.During the study period, the materials are three groups of pear seedlings.Two groups are respectively inoculated with a kind of AMF,but the third with nothing.These pear seedlings were kept in different concentration of aluminum stress environment.Through comparative analysis,We researched the physiological characteristics of pear seedlings inoculating with the different AMF in the same aluminum stress environment and the physiological characteristics of pear seedlings inoculating with the same AMF in the different aluminum stress environment. Results are as follows:1) Two kinds of AMF, Glomus mosseae (G.m for short) and Glomus intraradices (Gi for short), were used in this experiment.They infected the pear seedlings well.Mycorrhizal infection rate of G.i was greater than Gm.The highest mycorrhizal infection rate of G.i was 71.64%. Mycorrhizal dependence of G.i was greater than G.m, but the difference was not outstanding enough.2) Inoculating with AMF alleviated the damage of leaves’s number and area under Al stress,and promoted the pear seedlings biomass accumulation.But the impact on the pear seedlings diameter was not obvious.Inoculating with AMF significantly increased the root activity under low Al stress,also increased the total content of chlorophyll and carotenoid of leaves.Inoculating with AMF promoted photosynthesis of pear seedlings under low Al concentration,alleviated the leaves damage.In general, the effect on the pear seedling growth showed G.i was better than G.m.3) Inoculating with AMF increased the ability to absorb inorganic nutrients such as N、P、K,that indicated the formation of AM was favour of the accumulation of inorganic nutrients. By measuring the Al content in the pear seedlings showed that Al content was roots>stems>leaves.Though the sequestration of Glomalin-related proteins and adsorption of AM on Al, showed that Al was mainly concentrated in the roots of pear seedlings.Inoculating with AMF enhanced Al tolerance of pear seedlings.4) Both the content of MDA and the relative electrolytic leakage of pear leaves were reduced by inoculating with AMF, which alleviated the damage of leaf membrane permeability under Al stress.Inoculating with AMF also prevented large amounts of material leakage in the cell, reduced the damage degree of the pear seedlings membrane system, so that the stress resistance of pear seedlings was enhanced under Al stress.5)Under the stress of aluminium,Inoculating with AMF increased the soluble protein content of pear seedlings,that reduced the pressure of pear seedlings osmotic balance,and improved the ability of pear seedlings osmotic adjustment.The improvement of soluble sugar content increased the metabolism enzymes activity of pear seedlings.6)Soil enzyme,an important biological indicator for evaluation of soil environment,can be used to detect the pollution and fertility of the soil.All of the urease^ phosphatase and sucrase inside the soil,where was nearby the root of infected pear seedlings were higher than the matched group.In addition,the activity of urease and sucrase of the pear seedlings which inoculated with G.i was higher than those inoculated with G.m,but the difference was not significant.The increasing of soil enzyme promoted the pear seedlings to absorb nutrient substance.Al-tolerance of the pear seedlings were increased.7) GRSP is the protein which is secreted into the soil by AMF.Research showed that the content of GRSP was decreased under Al stress but increased by inoculating with AMF. So inoculating with AMF increased the content of GRSP.The GRSP and Al produced chelation each other, that promoted the Al to be fixed,reduced the content of Al inside the roots.