| Heavy metal lead significantly affected the normal growth anddevelopment as well as physiological metabolism of plant.Bioremediation has become one of the main methods of relieving thestress of heavy metal. Bacillus subtilis is one of the dominantmicroorganisms in the soil and plant. In contamination of heavymetals, B. subtilis could promot the growth and development of plant.Different strains have different promotion to crops under heavy metalstress. In the present study, wheat cultivar (Linfeng3) was used toinvestigate the changes of seed germination and seedling growth inresponse to different concentrations of Pb2+and B. subtilis QM3treatment, which was not only provide the theoretical basis for theresearch of relief technology for lead poisoning, but also lay thetheoretical foundation and provide technical support for thedevelopment of B. subtilis QM3in agricultural new applications. Themain results and conlusions were as follows:(1)Heavy metal Pb had inhibitory effect on seed germination of wheat. Pb stress could significantly reduce the germination rate,germination potential, germination index and vigor index, shoot androot length, root total surface area, root total volume and the activityof amylase were also reduced. The inhibition increased with theincrease of Pb2+concentration. Soaked with B. subtilis QM3couldalleviate the inhibiton of seed germination under Pb2+stress. Whenthe concentration of Pb2+was low, soaked with B. subtilis QM3hadsignificantly promoted various indexes of seed germination (P<0.05).When the concentration of Pb2+was2000mg/L, soaked with106CFU/mL B.subtilis QM3could make the germination rate, germinationpotential and germination index increased by68.57%,44.93%and51.32%respectively (P<0.05).(2)Heavy metal Pb had inhibitory effect on photosynthetic system ofwheat leaves. Pb stress could significantly decrease of chlorophyllcontent, Fv/Fm and Fv/F0, Pn, Tr and Gs, and Ci was increased inwheat leaves. Soaked with B. subtilis QM3could significantly promotephotosynthesis of wheat leaves under Pb2+stress. When theconcentration of Pb2+was50mg/L,106CFU/mL B.subtilis QM3couldmake the content of chlorophyll a, chlorophyll b, total chlorophyllincreased by14.7%,57.24%and33.6%respectively (P<0.05), butthere had no significant changes on Fv/Fm and Fv/F0, Pn, Tr and Gs(P>0.05). Under higher concentration of Pb2+stress, soaked with B.subtilis QM3could significantly increase the chlorophyll content,Fv/F0, Pn and Ci, but there had no significant influence on Tr and Gsand Fv/Fm (P>0.05).(3)The content of Pro was increased by Pb2+in wheat seedlings,soluble protein content was decreased first, and then increased. Thecontent of souble sugar was increased under high Pb2+stress. Inaddition, MDA content of wheat seedlings was increased with theconcentration of Pb2+. Soaked with B. subtilis QM3significantlydecreased the contents of Pro, soluble protein, souble sugar and MDA.When there was no Pb2+stress, soaked with B. subtilis QM3couldsignificantly decrease the content of MDA and soluble protein(P<0.05), but there had no significant influence on Pro and solublesugar content (P>0.05). Under Pb2+stress, soaked with B. subtilis QM3could significantly decrease the content of osmotic adjustmentsubstances (P<0.05).(4)Pb stress could enhance the activity of CAT, but the activities ofSOD, POD and APX were decreased with the increase of Pb2+stressconcentration. Soaked with B. subtilis QM3could increase theactivities of SOD, POD, CAT and APX. When there was no Pb2+stress,soaked with B. subtilis QM3could significantly increase the activitiesof SOD, POD and CAT of wheat seedlings (P<0.05), but there had nosignificant influence on the activity of APX (P>0.05). Under low concentrations of Pb2+stress, soaked with B. subtilis QM3couldsignificantly increase the activity of antioxidase (P<0.05). But it hadno significant effect on activity of antioxidase under high Pb2+stress. |
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