Effect Of Arbuscular Mycorrhizal Fungi On Cadmium Hyperaccumulation In Sedum Plumbizincicola

At present,among the remediation methods of cadmium-contaminated soil,hyperaccumulation plants to extract cadmium from soil is the most ecologically sound method to remediate soil cadmium pollution.However,hyperaccumulator generally have problems such as slow growth and small above-ground biomass,which limit their remediation effects.In order to further improve the effect of hyperaccumulation phytoremediation,it has become a new trend in the development of bioremediation of cadmium-contaminated soil by using microorganisms and hyperaccumulation phytoremediation to improve the effect of hyperaccumulation phytoremediation.In this study,Sedum plumbizincicola and the widely distributed arbuscular arbuscularmycorrhizal fungi（Rhizophagus intraradices,Funneliformis mosseae）from the soil were used as the main objects.A pot experiment was conducted to investigate the symbiotic properties of the arbuscular arbuscular mycorrhizal fungi and S.plumbizincicola,the effects of the arbuscular arbuscular mycorrhizal fungi on the uptake,transport and storage of cadmium in the S.plumbizincicola and the resistance mechanism.The study showed that all three species of arbuscular mycorrhizal fungi were highly resistant to Cd,and their infestation rate was still above 10%when the soil Cd content reached 80 mg·k^g-1.With the increase of soil cadmium content,the infestation rate of the root segment of S.plumbizincicola showed a trend of increasing first and then decreasing.The low concentration of cadmium stimulated the growth of arbuscular mycorrhizal fungi and the infestation rate of root segments reached 73%-75%.With the increase of soil cadmium content,the biomass of the upper part of the uninoculated associated mineral landscape increased.Inoculation with arbuscular mycorrhizal fungi increased the biomass of the upper part of the associated mineral landscape by 7%-58%.The lifting effect of R.intraradices was stronger than that of F.mosseae-1 and F.mosseae-2.Inoculation with arbuscular mycorrhizal fungi did not increase the phosphorus concentration in the leaves of S.plumbizincicola.The phosphorus content of S.plumbizincicola leaves decreased with increasing cadmium content,and inoculation with arbuscular mycorrhizal fungi resulted in a 4%-21%decrease in phosphorus content.Inoculation of F.mosseae-1 at high soil cadmium levels(40 and 80 mg·k^g-1)increased root and stem cadmium content,while decreasing leaf cadmium content and changing the storage location of cadmium in S.plumbizincicola.Inoculation of F.mosseae-2 and R.intraradices reduced cadmium uptake by S.plumbizincicola.With the increase of cadmium content,the cadmium enrichment factor of S.plumbizincicola decreased from 80 to 20 on average.The increase in biomass in the upper part of the associated skarn did not offset the decrease in enrichment capacity.Inoculation with F.mosseae-1 resulted in a 28%-77%decrease in Cd extraction from S.plumbizincicola,inoculation with F.mosseae-2 resulted in a 15.1%-30.98%decrease in Cd extraction,and inoculation with R.intraradices resulted in a 38%-62%decrease in Cd extraction.Inoculation with F.mosseae-1 resulted in 52%-102%increase in reduced ascorbic acid content of S.plumbizincicola leaves,inoculation with F.mosseae-2 in 43%-57%,and inoculation with R.intraradices in 27%-55%.Inoculation with arbuscular mycorrhizal fungi alleviated oxidative stress in S.plumbizincicola cells at higher soil Cd,resulting in a13%-33%decrease in leaf malondialdehyde content.The arbuscular mycorrhizal fungi increased SOD,CAT,G-POD and APX activities.Soil Cd content up to 80 mg·k^g-1,the arbuscular mycorrhizal fungi of the cluster did not significantly increase SOD,CAT,and G-POD activities,and even decreased CAT activity.In all treatments,the proportional size of cadmium content in each fraction of stem and leaf cells of S.plumbizincicola was:cell wall（F3）>soluble fraction（F2）>organelle and membrane（F3）.Among them,the proportion of cadmium in the cell wall of leaves was in the range of 50%-60%,and the proportion of cadmium in the soluble fraction was in the range of 20%-30%;the proportion of cadmium in each cell wall of stems was in the range of 40%-50%,and the proportion of cadmium in the soluble fraction was in the range of30%-40%.The inoculation of arbuscular mycorrhizal fungi did not cause significant changes in the cell wall cadmium,reduced the organelle and membrane cadmium,and increased the soluble fraction cadmium.The cadmium in the stems and leaves of S.plumbizincicola was mainly in the sodium chloride extracted state and the water extracted state,which together accounted for more than 70%,followed by 80%ethanol extracted state and acetic acid extracted state cadmium,and the other forms accounted for less.Inoculation with arbuscular mycorrhizal fungi increased the proportion of cadmium in the sodium chloride extracted state and the acetic acid extracted state.