Effects Of Four Ectomycorrhizal Fungi On Lead Resistance Of Pinus Tabulaeformis

In this paper,a liquid pure culture experiment was conducted to determine the lead resistance of four ectomycorrhizal fungi,Suillus luteus（Sl）,S.grevillei（Sg）,Gomphidius viscidus（Gv）,and Boletus sp.,（B.sp.）under lead stress.Then the pot experiments were conducted to study the growth,photosynthetic pigment content,antioxidant enzyme activity,and Pb absorption and distribution of Pinus tabulaeformis inoculated with ECMF under Pb stress.The main findings are as follows:1. Lead tolerance of ECMF strainsUnder the static culture of MMN liquid medium,the tolerance of 4 ECMFs at different Pb²⁺concentrations（0,10,30,50,100 and 200 mg/L）was studied.The results showed that the 4 ECMFs all had tolerance to Pb:The resistance of four ECMFs to lead is:B.sp.>Sg>Sl>Gv.The four ECMFs have a certain tolerance to Pb,and the tolerance levels are:B.sp.>Sg>Sl>Gv;at each Pb²⁺concentration,the dry weight and the content of mycelium of Sg,Sl and Gv all were Sg>Sl>Gv,the dry weight of B.sp.mycelium was higher than the other three fungi,and the lead content was lower than them.This indicates that B.sp.may improve its own resistance to lead by preventing or reducing Pb2+from entering the fungal cells,while Sg,Sl,and Gv improve lead resistance by tolerating high concentrations of lead in the mycelium.2. The effect of ECMF on the growth of Pinus tabulaeformis and Pb absorption and distributionThe infection rate of Sg and Sl to P.tabulaeformis seedlings under Pb stress was higher than that of Gv and B.sp.,Sg inoculation significantly increased the biomass of the aboveground and root of P.tabulaeformis,followed by Sl,the other two kinds of inoculation treatment and non-inoculation treatment were no significant difference,indicating that the increased infection rate enhanced the lead resistance of P.tabulaeformis.The content of chlorophyll a,chlorophyll b and carotenoid in Sg inoculated P.tabulaeformis increased by56.19%,30.89%and 75.00%respectively compared with the non-inoculation treatment,and the content of carotenoid in P.tabulaeformis inoculated with Sl increased by 50%.Among the four ECMFs,the above-ground/root Pb（concentration）transport coefficient inoculated with Sg was the smallest.Sg and Sl inoculation significantly increased the accumulation of Pb in the roots of P.tabulaeformis.Gv inoculation reduced the absorption and accumulation of Pb,indicating that Sg and Sl inoculation improve the ability of P.tabulaeformis to stabilize Pb.3. Effects of ECMF inoculation on the antioxidant capacity of Pinus tabulaeformis under Pb stressThe contents of hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）in the Sg-inoculated P.tabulaeformis ground were reduced by 37.12%and 51.44%respectively compared with the non-inoculated treatment;the H₂O₂and MDA in the Sl inoculated P.tabulaeformis ground were decreased by 21.42%And 42.07%.In addition,compared with the non-inoculation treatment,the four ECMF inoculations increased the SOD and POD activities of P.tabulaeformis aboveground,and the CAT activities of Sg and Sl inoculated aboveground P.tabulaeformis increased by 118.76%and 46.01%,respectively.The results showed that Sg and Sl inoculation alleviated the oxidative damage caused by Pb stress,and enhanced the activity of scavenging active oxygen by increasing the activity of antioxidant enzymes.