Influence Of Ectomycorrhizal Fungi On The Lead Tolerance Of Poplar And Related Mechanism

Soil heavy metal pollution has caused the enormous ecological problems, and endangers human health. The joint repair technology of plant-microbe has drawn more and more attentions of the researches. This paper studied the effects of two ectomycorrhizal fungi(ECMF) strains on lead tolerance of Populus cathayana. Furthermore, the effects of ECMF inoculation on the poplar physiological and biochemical characteristics, lead absorption and distribution, nutrient content, leaf P transport protein gene expression, rhizospheric soil pH and content of small molecule organic acid under lead stress were also studied in order to analyze the related mechanisms. The main results were listed as follows:1. Screening of poplar ECMF strains with high lead toleranceAfter being isolated from the fruiting bodies, ECMF strains were inoculated back to P. cathayana seedlings and suffered the lead tolerance screening. Finally, two poplar ECMF strains with higher lead tolerance were screened and identified as Calvatia gigantean and Thelephora sp. based on their morphological and molecular characteristics.2. Influence of ECMF on poplar lead toleranceUnder lead stress, ECMF strains could significantly increase the poplar height, biomass and root structure, and the effect was more apparent under higher lead stress, suggest that ECMF can improve the lead tolerance of poplar. Moreover, the improving effect of C.gigantean was bigger, that may be related to its higher colonization rate in the poplar roots.3. Improving mechanisms of ECMF on poplar lead toleranceECMF strains could reduce the lead damage to the plant, improve poplar lead tolerance so that promote their growth under the lead stress by improving the poplar net photosynthesis,chlorophyll content, leaf water use efficiency, activities of SOD and CAT, the absorption of phosphorus and leaf phosphorus transport protein gene expression, as well as by decreasing the leaf exosmosis conductivity. Although ECMF could increase the lead absorption of poplar,but lead mainly was accumulated in poplar roots and lead transfer to sensitive leaves was suppressed. Therefore, ECMF strains could also reduce lead damage to poplars by decreasing the lead content in up ground plant parts.