| With the industrial development,population explosion and acceleration of urbanization,heavy metal pollution becomes more and more severe in soil.The heavy metals contamination in soil could inhibit the crop growth and reduce the yields.The heavy metals could enter into the food chain by the crop's absorption and eventually threat the human health.This experimeant is one of the crop safety production studies. Purple soil from Sichuan Agricultural University were chosen for pot experiment.Zinc (Zn) and chromium(Cr) were added to the soil according to the national environmental quality standard (GB15618-1995)(dry land pH>7.5).The soybean was planted by root bag method.Soil respiratory intensity,microbial quantity, SMBC, SMBN, SMBP, URASE, CAT and INVERTASE of the rhizosphere and non-rhizosphere soil and the rhizosphere soil microbial diversity by PCR-DGGE were determined.On this basis,the change of the microbiology characteristics of the soybean soil under Zn and Cr stress was studied. Based on this,under Zn and Cr compound stress,the effects and discipline on microbial characteristics in rhizosphere and non-rhizosphere soil were revealed;meanwhile,this could provide theoretical basis for soybean production safety.The results were as follows:(1)The respiration of the rhizosphere soil was stronger than that of the non-rhizosphere soil. When Zn wasO and 100mg.kg'1,with the increase of the Cr concentration,the respiration of rhizosphere and non-rhizosphere soil increased first,and then decreased.When Zn was 250 and 500 mg.kg-1, with the increase of the Cr concentration,it gradually decreased.When Cr was 0 and 90mg.kg-1, with the increase of the Zn concentration,the respiration of rhizosphere and non-rhizosphere soil increased first,and then decreased. When Cr was 300 and 400mg.kg-1 with the increase of the Zn concentration,gradually decreased.(2)The bacteria was dominant in soybean soil followed by actinomycetes and fungi.When Zn was 0,100mg.kg-1,with the increase of the Cr,rhizosphere bacteria increased first,and then decreased;when Zn was 250 and 500 mg.kg-1,with the increase of the Cr,the bacteria gradually decreased.When Cr was 0 and 90mg.kg-1,with the increase of the Zn,bacteria showed an increase first and then a decrease;when Cr was 300 and 400 mg.kg-1, with the increase of the Zn,the bacteria gradually decreased. When Zn or Cr was 0 mg.kg-1, actinomycetes in rhizosphere soil and bacteria in non-rhizosphere demonstrated an increase first and then a decrease with the increase of Cr or Zn concentrations;when Zn was 100,250 and 500 mg.kg-1,with the increase of the Cr concentration,bacteria in the non-rhizosphere soil and the actinomycetes in rhizosphere soil showed a decrease;when Cr was 90,300 and 400 mg.kg-1, with the increase of Zn concentration, bacteria in the non-rhizosphere soil and the actinomycetes in rhizosphere showed a decrease. With the increase of the Zn and Cr,fungi in rhizosphere and non-rhizosphere soil gradually decreased.And the actinomycetes in non-rhizosphere soil decreased with the increase of the Zn or Cr concentration.(3)When Zn was 0 and 100 mg.kg-1,with the increase of Cr concentration,SMBC and SMBN in rhizosphere soil increased first and then decreased;when Zn was 250 and 500 mg.kg-1,SMBC and SMBN gradually decreased with the Cr increase.When the Cr concentration is certain,SMBC,SMBN and SMBP in rhizosphere and non-rhizosphere soil gradually decreased with the Zn increase. When the Zn is certain,SMBP in the rhizosphere soil gradually decreased with the Cr increase.When Zn was 0 mg.kg-1,SMBC and SMBN in non-rhizosphere soil increased first and then decreased with the Cr increase;when Zn was 250 and 500 mg.kg-1,SMBC and SMBN in non-rhizosphere soil gradually decreased with the Cr increase.(4) Soil enzyme activities in rhizosphere soil were higher than those in the non-rhizosphere soil.When Zn was certain, URASE in rhizosphere and non-rhizosphoere soil increased first and then decreased with the Cr increase;when Cr was 0 mg.kg-1, URASE in the rhizosphere and non-rhizosphoere soil increased first and then decreased with the Zn increase;when Cr was 90,300 and 400mg.kg-1,with the Zn increase, URASE in the rhizosphere and non-rhizosphoere soil decreased.When the Zn wasO mg.kg-1,CAT in the rhizosphere and non-rhizosphoere soil and I in the non-rhizosphoere soil increased first and then decreased with the Cr increase;when Zn was 100,250 and 500 mg.kg-1, URASE and INVERTASE in rhizosphere and non-rhizosphoere soil gradually decreased with the Cr increase.When Cr was certain,CAT in the non-rhizosphoere soil, URASE and INVERTASE in rhizosphere and non-rhizosphoere soil gradually decreased with the Zn increase.When Cr was 0 and 90 mg.kg-1,CAT in the rhizosphere soil increased first and then decreased with the Zn increase;when Cr was 300 and 400 mg.kg-1,that gradually decreased with the Zn increase.When Zn was 0 and 100 mg.kg-1, INVERTASE in the rhizosphere soil increased first and then decreased with the Cr increase;when Zn was 250 and 500 mg.kg-1,that gradually decreased with the Cr increase.(5) MQ in rhizosphere soil was weaker than that in the non-rhizosphere soil.When Zn was 0 and 100 mg.kg-1,MQ in rhizosphere and non-rhizosphere soil increased with the Cr increase;when Zn was 250 mg.kg-1, MQ in the rhizosphere soil increased first and then decreased with the Cr increase;when Zn was 500 mg.kg-1,MQ in the rhizosphere soil gradually decreased with the increase of Cr;when Zn was 250 and 500 mg.kg-1,MQ in the non-rhizosphere soil gradually decreased with the increase of Cr.When Cr was certain,MQ in rhizosphere and non-rhizosphere soil first increased and then decreased with the Zn increase.(6) The evenness of the fungi species was among 0.9494-0.9994.The cluster analysis found the similarity of all the sample fungi was among 37%-68%,which meant that the difference existed in fungi species structure.The evenness of the bacteria species(0.9857-0.9993) was very close,and the H was among 2.6368-3.2513.The similarity of the bacteria was 21%-80%,which meant the difference existed in bacteria species structure. |
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