Research On The Activation Of Insoluble Phosphorus By Ectomycorrhizal Fungi Under Acid Aluminum Stress

In forest soils in South China,more than 90%are acid and rich of aluminum.Aluminum can easily be activated into active aluminum in acid soil.it is toxic to plants.Forests are often restricted by widespread aluminum toxicity,and one of the toxic mechanisms of plants is to inhibit the absorption of phosphorus,which make the poor soil phosphorus deficient.Ectomycorrhizal fungi?ECMF?can form a mutualism system with most trees.It plays an important role in improving plant resistance to aluminum and absorption of phosphorus,and plays an important role in maintaining the healthy and sustainable development of forest ecosystem.However,it is not clear whether ectomycorrhiza can activate the insoluble phosphorus in the soil and promote the absorption and utilization of phosphorus in the host plant under acid aluminum stress.Therefore,this reasearchtreated aluminum resistance ability and promoting effect of Southwest China ECMF as mycorrhizal fungi inoculant,Lactarius delicious?Ld2 and Ld3?and Pisolithus tinctorius?Pt715?,and mixed them with the seeds of Pinus massoniana.We cultivated Pinus massoniana under acid aluminum stress for a period of time,then We detected and analyzed the morphological changes of inorganic insoluble phosphorus in rhizosphere soil,as well as the absorption and utilization of phosphorus by host plants.In order to explore the activation and utilization of ectomycorrhizal to inorganic insoluble phosphorus under acidic aluminum stress and select the ectomycorrhizal fungi of resistance?tolerance?of aluminum and absorption of phosphate ability,which will provide theoretical and practical basis for the application of ectomycorrhizal technology in afforestation and ecological restoration of acid aluminum rich forest land in China.The main conclusions were as follows:?i?The three ECMF and Pinus massoniana seedlingscan form a good symbiotic relationship and significantly promoted growth and utilization of inorganic insoluble phosphorus sources of Pinus massoniana under acid Al stress.The average biomass of mycorrhizal seedlings than non-mycorrhizal seedlings was higher than that of 9.83%¹6.55%.ECMF improved the capacity of Pinus massoniana growth ranked asLd3>Ld2>Pt715.And the root shoot ratio of mycorrhizal seedlings significantly decreased,which was conducive to more photosynthate distribution to the aboveground parts and increase the yield of trees.Mycorrhizal seedlings biomass,seedling height and ground diameter overall showedlarger on the soluble phosphorus source of Fe-P and Al-P under Al stress,which showed insoluble phosphorus source promotes mycorrhizal seedlings growth,and no matter what the source of phosphorus treatment,the growth of Ld3 is better than Ld2 and Pt715.?ii?Under acid Al stress,inoculation of ECMF to improve the content of phosphorus,potassium,magnesium and calcium in the whole,especially to promote the absorption and transport of phosphorus and calcium.And it mainly alleviated aluminum toxicity by inhibitingthe uplink ofaluminum.The average phosphorus content of three mycorrhizal seedlings were Ld3=Ld2>Pt715,and aluminum contentwerePt715>Ld2>Ld3,which means two linesof Lactarius delicious element absorption of phosphorus and aluminum resistance ability was better than Pt715,and aluminum resistance effect of Ld3 was better.Under acid Al stress,insoluble phosphorus treatment of mycorrhizal seedlings were higher than that of P₀ treatment about the content of calcium,phosphorus and potassium,and the aluminum content was less than P₀,which indicated that inoculating ECMF of Pinus massoniana could better use the existing acidic soil insoluble inorganic phosphorus source,including Fe-P and Al-P.Al stress,The content of K,Mg and Ca in the mycorrhizal seedlings treated by Al-P was higher than that of Fe-P treatment,but the Fe-P treated mycorrhizal seedlings were more capable of transporting phosphorus.At the same time,under the treatment of Fe-P mycorrhiza on Al absorption and transport capacity was lower than Al-P treatment.?iii?The correlation analysis showed that there was positive correlation between the content of K,Mg,P and Ca of three mycorrhizal seedlings?p<0.01?,which indicated the synergistic effects between the four.While the content of P,K,Mg and Ca had significant negative correlation with Al?p<0.01?,which indicated that Al can inhibit absorption of mycorrhizal seedlings on P,K,Ca,Mg.?iv?Compared with non-mycorrhizal seedlings,the pH value of rhizosphere soil of mycorrhizal seedlings significantly decreased.Under acid Al stress,mycorrhizal seedlings rhizosphere soil pH value of Fe-P and Al-P treatments were lower than P₀ treatment,which showed that indicated that mycorrhizal promoted the secretion of H⁺in rhizosphere,and under the condition of acid aluminum stress,the treatment of poorly soluble phosphorus increased the H⁺secretion of mycorrhizal seedlings.?v?Inoculation of ECMF significantly promoted the transformation of inorganic insoluble phosphorus to phosphorus in rhizosphere soil of Pinus massoniana seedlings.Their the average content of available phosphorusin the rhizosphere soil than non mycorrhizal seedlings was higher than of 130%¹57%.Underacid Al stress,the content of available phosphorus in rhizosphere soil of Pinus massoniana decreased significantly.The decreasing of non mycorrhizal seedlings was large,falling by 96%.While the content of available phosphorus in mycorrhizal seedlings were significantly higher than non mycorrhizal seedlings.The content of available phosphorus in rhizosphere soil of Pinus massoniana ranked as Ld3>Ld2>Pt715,andtheir content are the highest under Fe-P treatment.?vi?The proportion of inorganic phosphorus in rhizosphere soil of Pinus massoniana increased by the addition of aluminum.But inoculation of three ECMF could promote the activation of inorganic soluble phosphorus in rhizosphere soil,and the effects varied from isolates.Inoculation with Ld2 mainly activated Fe-P,andPt715 couldsinificantly activated Al-P,and Ld3 could activated Fe-P and Al-P Ca-P.And the growth of O-P in rhizosphere of Ld3 mycorrhizal seedlings was the smallest.At the same time compared with the P₀ treatment,insoluble phosphorus sources can promote mycorrhizal seedlings to activate insoluble phosphate in soil.The ability of Ld3 and Ld2mycorrhiza was stronger than Pt715 in insoluble phosphorus utilization.Theyare more suitable for the utilization of insoluble phosphate in acid soil Pinus massoniana.In summary,under acid aluminum stress,inoculation of Ld2,Ld3 and Pt715 significantly promoted the growth of Pinus massoniana seedlings and the use of Al-P and Fe-P for inorganic soluble phosphorus sources,which was beneficial to the distribution of photosynthate to the upper part of the ground.Three kinds of mycorrhizal seedlings in the root,with the best effect of Ld3,Ld2,Pt715 is relatively weak.The infection of 3 kinds of ECMF significantly increased the absorption and transport of phosphorus,potassium,calcium and magnesium,especially phosphorus and calcium,and inhibition of the uplink of aluminum,promoted the secretion of H⁺in the rhizosphere,and the transformation of the insoluble phosphorus to the effective phosphorus.Therefore,inoculation of Ld2,Ld3 and Pt715 under acid aluminum stress can improve the bioavailability of inorganic soluble phosphorus sources in rhizosphere soil of Pinus massoniana seedlings,and H⁺may play an important role.