Effccts Of Inoculation With Paenibacillus Mucilaginosus On The Absorption Characyeristics Of Heavy Metals In Plants In Leguminous And Gramineous Intercopping Systems

With the rapid development of human society,more and more heavy metals enter the soil,and the pollution of heavy metals in the soil becomes more and more serious.Heavy metal pollution in soil can threaten plant seriously,destroy the normal physiological functions of plants,reduce crop production and grain income.Heavy metals in soil can also be transferred to human body through the transmission of food chain,which brings harm to human survival and health,therefore,the study of soil remediation technology is of great significance to the healthy development to human.Taking the polluted soil in lead-zinc mining area as the research object,the effects of Paenibacillus mucilaginosus ACCC10013 inoculation and different root segregation modes on plant growth and heavy metal uptake characteristics were studied by pot experiment using the intercropping model of leguminous alfalfa?Medicago sativa L.?and ryegrass?Lolium perenne L.?.The response mechanism of plants to heavy metal stress under intercropping-inoculation system was discussed,and the effects of different root barrier methods on heavy metal absorption characteristics of plants were revealed.The main results are as follows:1.Under heavy metal stress,intercropping can increase the growth and development of alfalfa and ryegrass,plant height,root length,biomass,chlorophyll synthesis in leaves,nitrogen uptake,and inoculation of Bacillus colloides on the basis of intercropping can further promote plant growth.Under moderate pollution conditions,the biomass of shoot and root of Alfalfa increased by 29%and 33%respectively,and after intercropping inoculation,the biomass of shoot and root of Alfalfa under intercropping system increased by 44%and 38%respectively.Plants planted in highly polluted soils were significantly more inhibited by heavy metals than those planted in moderately polluted soils.Intercropping can significantly reduce the content of Pb and Cd in alfalfa and ryegrass tissues,and the inhibition effect of intercropping on the absorption of Pb and Cd in plants under moderate pollution conditions is greater than that under extreme pollution conditions.Under moderately polluted conditions,the intercropping treatment significantly reduced the Pb content in the shoot of alfalfa and ryerass by 31%and 22%respectively,and the intercropping treatment reduced the Cd content in the shoot of alfalfa and ryegrass by 33%and 10%respectively.The contents of Pb and Cd in alfalfa and ryegrass decreased to the lowest level after intercropping-inoculation treatment.The contents and total uptakes of Pb and Cd in plants planted under extremely polluted conditions were significantly higher than those under moderately polluted conditions.2.Under moderate pollution conditions,intercropping treatment can significantly reduce the oxidative damage in alfalfa,and intercropping can significantly reduce the O.₂^-and H₂O₂of the shoot and root of alfalfa by 22%,17%and 29%,24%respectively.Under extremely polluted conditions,indirect inoculation could reduce the oxidative damage of alfalfa and ryegrass.After inoculation,the MDA content in the shoot of alfalfa and ryegrass under intercropping system decreased by 25%and 16%respectively.The oxidative damage of alfalfa and ryegrass reached the lowest value under the treatment of intercropping-inoculation.Under moderate pollution conditions,intercropping could significantly increase the antioxidant enzymes activities of alfalfa and ryegrass,and reached the maximum after inoculating bacteria on the basis of intercropping.3.The plant height,root length and biomass of alfalfa and ryegrass decreased with the increase of root barrier effect,compared with no root barrier,the strainer root barrier significantly reduced the biomass of the shoot of the alfalfa and ryegrass by 36%and 28%respectively.The increase in root barrier effect inhibits the synthesis of chlorophyll and the absorption of nitrogen in the root of alfalfa and ryegrass.The strainer root barrier resulted in a significant reduction in the chlorophyll content of alfalfa and ryegrass by 18%and 18%respectively,and the plexiglass root barrier of the chlorophyll content of alfalfa and ryegrass was significantly reduced by 16%and 19%respectively compared to the membrane root barrier.4.The contents of Pb and Cd in alfalfa and ryegrass increased with the intensification of root barrier effect.Compared with non-segregation,complete segregation significantly increased the contents of Pb and Cd in the shoot of alfalfa by 32%and 77%,respectively.The oxidative stress in alfalfa and ryegrass increased with the increase of root blocking effect.The activity of antioxidant enzymes in alfalfa and ryegrass decreased with the increase of root barrier effect,SOD,POD and CAT in plants decreased with the increase of root barrier effect.Soil solution is the main factor of heavy metal pollution to ryegrass under intercropping conditions.