Effects Of Intercropping On Cadmium Uptake And Transport By Wheat And Accumulators

With the rapid increase in the development and utilization of mineral resources by humans,a large amount of cadmium?Cd?is brought into the soil with industrial waste,which leads to potential harm for soil ecosystems and agricultural products.The technology of Cd accumulators and crops intercropping is widely concerned for its low cost and easy operation.The interaction between accumulators and crops is very complicated in intercropping systems.It is of great theoretical and practical significance to reveal the interrelationships among the rhizosphere environment,microbial community structure,and the bioavailability of heavy metals in the accumulator-crop intercropping system.In this study,differences in Cd uptake and translocation,changes in rhizosphere environment,the bacterial community in rhizosphere,growth and root cell ultrastructure of wheat were investigated under intercropping wheat with Cd accumulators,to establish the theoretical foundation for efficient phytoremediation technologies for Cd-contaminated soils,the utilization of Cd-contaminated farmland and crop safety production.The main results include:?1?Compared with Amaranthus mangostanus L.,Lolium perenne L.,Solanum nigrum L.has a stronger Cd uptake and translocation capacity,which can be used as ideal plant material for remediation of Cd contaminated soil.Intercropping with wheat promoted the growth of the accumulators,and the Cd accumulation in shoots of three accumulators increased by 23.36%?69.87%.Therefore,the Cd extraction efficiency of the three accumulators was improved.Intercropping with three accumulators promoted the absorption of Cd in shoots of wheat and increased the risk of excessive Cd concentration in wheat.?2?The bacterial relative abundance of phyla was different under different planting patterns,but the dominant phyla in the rhizosphere were similar.More than 75.0%of the bacterial sequences in the rhizosphere belonged to Acidobacteria,Proteobacteria,Bacteroidetes,Actinobacteria,and Chloroflexi under different treatments.Alpha diversity and principal component analysis?PCA?showed that there was no significant difference in the total amount of bacteria in the rhizosphere of monoculture and intercropping Solanum nigrum L..Intercropping with Solanum nigrum L.changed the rhizosphere environment of wheat,and had a significant effect on the bacterial community.The total number and diversity of wheat rhizosphere soil bacteria decreased,leading to a decrease of urease?UA?,alkaline phosphatase?ALP?,catalase activity?CAT?.?3?Solanum nigrum L.and wheat intercropping in a hydroponic system,compared with monoculture wheat,the Cd concentration in the roots of intercropping wheat decreased by 28.30%?47.20%.And the accumulation of Cd decreased by 10.08%?32.43%,which was treated with 20,40,60?mol·L^-1 Cd.However,the Cd accumulation of wheat shoots was no significant difference under different planting patterns.There were fewer Cd electron-dense particles of wheat root cells under intercropping with Solanum nigrum L.,which led to less toxicity on the wheat root cell membrane and nuclear membrane.In summary,intercropping with Solanum nigrum L.inhibited the absorption of Cd by wheat roots and reduced the damage to root cells under the hydroponic intercropping system.Under the soil-cultured intercropping system,the total number and diversity in the rhizosphere bacteria of wheat decreased,the Cd accumulation in wheat increased,the Cd extraction efficiency of Solanum nigrum L.increased.