Study On Potassium Absorption Characteristics Of Ectomycorrhizal Fungi

Ectomycorrhizal fungi,an important group of soil microorganisms which ubiquitously exists in nature,play significant ecological roles.Selected ectomycorrhizal fungi could benefit to the growth and nutrition of the host plants,as well as their resistance to drought,salt and diseases.Potassium,next only to nitrogen in amount,is one of the essential major nutrient elements for trees.Lack of potassium may cause serious negative effects on growth and development of trees. Potassium absorption by trees drops significantly in heavy metal polluted soils.However,when inoculated by ectomycorrhizal fungi,absorption of potassium by trees enhanced remarkably, including water-soluble K,exchangeable K and slowly available K in soil.In the present experiments,four ectomycorrhizal fungi strains(three strains of Lactarius deliciosus Ld-1,Ld-2,Ld-3,isolated from soils under Pinus Massoniana forest on Jinyun Mountain,Chongqing,2002,and Pisolithus tinctorius 715,isolated from an eucalyptus in red soil at Xichang,1996),were selected to investigate:(â…°)absorption of K in pure culture;(â…±)absorptive character of K under different concentrations of Hg and Cd;(â…²)kinetics of K absorption under different concentrations of K.Results are as below:1.The four ectomycorrhizal fungi are cultured for 14 days in the normal Potassium content of the liquid medium Pachlewski.Ld-1 not only grow the fastest and the growth is also the best.The four ectomycorrhizal fungus biomass is:Ld-1＞Ld-2＞Pt715＞Ld-32.The four ectomycorrhizal fungi are cultured for 14 days in the culture medium with different concentrations of Potassium.With the Potassium concentration of the liquid medium increased,the Potassium content of the four ectomycorrhizal fungi body heighten.3.The influence that the biomsa varity of the four ectomycorrhizal fungi isn't significantly in liquid medium Pachlewski contained Mercury.Only Ld-1's biomass decreases significantly under middle and high concentration of Mercury,but the other's biomass isn't significantly varied.4.Mercury can affect significantly the Potassium content of the four tested ectomycorrhizal fungi. Overall,in the four different treatments of the concentration of Mercury,the four tested ectomycorrhizal fungi's the average Potsssium content in turn is:Pt715＞Ld-3＞Ld-1＞Ld-2.With the concentration of mercury increased,the Potassium content of Pt715's mycelium significantly decreases;Under the low concentrations of Mercury,the Potassium content of Ld-1 and Ld-2's mycelium significantly increase,and under the middle concentrations of Mercury,the Potassium content of Ld-3's mycelium significantly increase.5.Cadmium cann't affect significantly the biomass of Pt715 and Ld-3;Cadmium affect significantly the biomass of Ld-1 and Ld-2,but under the low concentrations of Cadmium,its biomass significantly increase.With Cadmium polluted,the average biomass of the mycelium in turn is:Ld-1＞Ld-2＞Pt715＞Ld-3.6.Cadmium affect significantly the Potassium content of the four tested ectomycorrhizal fungi. Under the four different treatments of the concentration of Cadmium,the four tested ectomycorrhizal fungi's the average Potsssium content in turn is:Ld-1＞Pt715＞Ld-2＞Ld-3.With the concentration of Cadmium increased,the Potassium content of Pt715's mycelium significantly decreases;Compared to blank treatment,under the low,middle and high concentration of Cadmium, the Potassium content of Ld-1 increase significantly,and the content of Potassium under the low concentration of Cadmium is the highest(22.47%).Under the low and middle concentration of Cadmium,the Potassium content of Ld-2 significantly increase,the Potassium content of Ld-3 significantly increase,under the low-Cadmium.7.In the absence of heavy metal pollution conditions,the four tested ectomycorrhizal fungi's dynamic parameters of K⁺ absorption have significant differences.K_m:Ld-2＞Ld-1＞Ld-3＞Pt715;I_max:Ld-3≥Ld-2＞Pt715＞Ld-1;C_min:Ld-2＞Ld-1≥Ld-3＞Pt715;Compared with the other ectomycorrhizal fungi,K_m and I_maxof Pt715 are lower.It illustrated that Pt715 was suitable for the low-Potassium nutrient soil environment;K_m and I_maxof Ld-2 are higher,that illustrated Ld-2 was suitable for the high-Potassium nutrient soil environment;For Ld-3,its K_m is low and its I_maxis high,it illustrated Ld-3 was suitable for the any Potassium nutrient soil environment;But the C_minof Pt715 is minimum in the four tested ectomycorrhizal fungi,it illustrated Pt715's absorbent concentration of Potassium was the lowest.8.Mercury significantly inhibits the ectomycorrhizal fungi's the absorption rate,the absorption speed and minimum absorbent concentration,the higher the concentration of Mercury,the greater the inhibition;For different ectomycorrhizal fungi,the effect is different;However,the appropriate concentration of Mercury can increase the ectomycorrhizal fungi's the Potassium absorption rate,the Potassium absorption speed and the minimum Potassium absorbent concentration,as Ld-2 under low and middle Mercury concentration;the excessive concentration of Mercury can decrease the ectomycorrhizal fungi's the Potassium absorption rate,the Potassium absorption speed and the minimum Potassium absorbent concentration.9.The same as Mercury,Cadmium significantly inhibits the ectomycorrhizal fungi's the Potassium absorption rate,the Potassium absorption speed and the Potassium minimum absorbent concentration,the higher the concentration of Mercury,the greater the inhibition;For different ectomycorrhizal fungi,the effect is different;the appropriate concentration of Mercury can increase the ectomycorrhizal fungi's the absorption rate,the absorption speed and the Potassium minimum absorbent concentration,as Ld-2 and Ld-3 under low Cadmium concentration;the excessive concentration of Cadmium can decrease the ectomycorrhizal fungi's the absorption rate,the absorption speed and the Potassium minimum absorbent concentration.