Effects Of Copper Stress On Growth Of Amaranthus Mangostanus L. Seedlings,Soil Physicochemical Properties And Soil Bacterial Community

Copper is the third most used metal in the world and is one of the essential trace metals for humans,animals and plants.However,with the precipitating of industrialization process,the issue of soil copper pollution is increasingly common in our country,which causes all kinds of soil safety problems.Phytoremediation is the most effective and environmentally friendly method to control copper contaminated soil.Therefore,this research took Amaranthus mangostanus L.as the research object and set six soil copper concentration levels of 0（control group）,60,120,400,1000and 2000 mg/kg by adding CuSO₄to the soil,to explore the effects of copper stress on the growth of Amaranth seedlings,soil physical and chemical properties and soil bacterial community,in order to provide reference for the phytoremediation of Cu-polluted soil.The results showed that:（1）When the concentration of Cu was less than 400 mg/kg,the height,root length,leaf area and biomass of amaranth were promoted,while when the concentration of Cu was more than 400 mg/kg,the plant height,leaf area and biomass of Amaranth were inhibited.Otherwise,the growth rate and root tolerance coefficient of amaranth showed an upward trend at first and then a downward trend with the increase of the concentration of exogenous copper,and both achieved the highest value of 0.118 and 1.23 respectively under the treatment of 120 mg/kg copper concentration.（2）The copper content in amaranth root was much higher than that in stem and leaves,and it raised with the increment of copper concentration.When the Cu-concentration was 2000 mg/kg,it reached the maximum value of 290.7 mg/kg,indicating that amaranth had a certain enrichment ability for soil copper.However,the copper content in stems and leaves reached the climax of 45.5 mg/kg and 36.7 mg/kg at 400 mg/kg copper treatment,although no obvious toxic symptoms were shown,but the copper content did not continue to increase.（3）Soil pH,total nitrogen content and cation exchange capacity were remarkably reduced by exogenous Cu addition,and there was a notably negative correlation between these three indexes and Cu concentration（p<0.05）,with the correlation coefficients being 0.958,0.985 and 0.902,respectively.The soil total phosphorus content increased obviously with the increment of Cu-concentration,and the correlation coefficient between the two reached 0.954 at the level of 0.05.（4）The richness and diversity of soil bacterial community will downgrade when exogenous copper is added to the soil.The research also showed that Proteobacteria,Bacteroidota,Acidobacteriota,Actinobacteriota,Halobacterota,Gemmatimonadota,Planctomycetota,Verrucomicrobiota,and Chloroflexi were the dominant phyla that constitute soil bacterial community structure,among which,The relative abundance of Proteobacteria ascended with the increment of soil Cu-concentration,and there was a significant positive correlation with soil copper concentration（p<0.05）.However,Acidobacteria,blastomonas and pontosporum showed the opposite trend,and there was a significant negative correlation between soil copper concentration（p<0.05）.These results indicated that Cu has a poisonous influence on plants,it can also alter soil physical and chemical properties and impact soil bacterial community,and the variation of soil environment can also further influence the natural development of amaranth.For this reason,when plants are used to repair soil contaminated by HMs,the soil physical and chemical properties and the repercussion of soil microorganisms to HMs should also be paid attention to.