| With the development of industry,environmental pollution becomes more and more serious,especially soil ontamination.Exploit energy plant on heavy metal polluted soil can not only make contaminated soil useful,reduce the competition for grain land,bring some economic effect,but also improve the condition of heavy metal polluted soil.The energy plant hemp(Cannabis sativa L.)is a kind of large bimass and easy to plant,which has high economic value plant.This research,a hydroponic experiment carried out to check the effect of the application methods and different plant growth promoting bacterias(PsJN?Jp3-3?J62).Pot experiment was to research the hemp growth promoted effect by plant growth promoting bacteria under heavy metal stress.(1)Hydroponic experiment carried out with the seeds soaking inoculated with PGPB PsJN in the cadmium(Cd)concentration gradient 0,25,50,75,100 ?mol/L.The results showed that with the increasing concentration of cadmium,the biomass of Yunma 4 showed significantly decreased while the accumulation of cadmium increased.Strain PsJN demonstrated obvious promoting effects(incluing shoot length,root length,shoot fresh weight,shoot dry weight,root fresh weight,root dry weight,and root activity,root morphology)of Yunma 4 under lower cadmium stress(p<0.05).But the results also demostrated that when the cadmium concentration over 50?mol/L,PsJN had not a significant promoting effect.The fresh root weight and dry root weight of EC50,iioculated with PsJN are 99.16?mol/L and 175.36?mol/L,showed much higher compared with the control which are 89.24?mol/L ? 135.70?mol/L respectively.It means that the bacteria PsJN improve the tolerant ability of hemp under cadmium stress.(2)PGPB(PsJN,Jp3-3,J62)inoculation with different application methods(soaking seeds,foliar spraying,root spraying)in the hydroponic experiments carried out in the cadmium stress 50?mol/L.The results showed that soaking seeds to inoculate bacteria had a better promoting effect(p<0.05)on both the growth of hemp and also on the accumulation of cadmium.On the other hand,for foliar spraying,PsJN?Jp3-3 had a better influence on the shoot part but little effect was found on the root of hemp Yunma 4.Foliar spraying J62 didn't show obvious influence on the growth of Yunma 4.Root spraying PsJN?Jp3-3 inoculation showed obvious effect(p<0.05)on the root growth of Yunma 4 while no significant effect was found the aboveground of Yunma 4.Different plant growth promoting bacteria had significant effect(p<0.05)on biomass parameters(shoot height,root length,shoot fresh weight,shoot dry weight,root fresh weight,root dry weight).The application methods had significant effect(p<0.05)on shoot height,shoot fresh weight,shoot dry weight,root fresh weight while no significant effect(p>0.05)on root length and root dry weight.The interaction of plant growth promoting bacteria and application methods showed significant effect(p<0.05)on shoot fresh weight,but no significant effect was found on other biomass parameters.(3)Soil culture experiment which use soaking seeds for inoculation carried out in the laboratory using heavy metal polluted soil from Zhuzhou.The results showed that strain PsJN,Jp3-3,J62 all have significant effects(p<0.05)on the growth of two hemp seedlings(Yunma 4 and Lu'an).At the same time,those PGPB strains showed obvious promoting effect on the accumulation of heavy metal in different levels.The content of heavy metal in the leaves and stems of Yunma4 demonstrated higher than that of Lu'an while the two hemp cultivars have similar heavy metal content of the root,this maybe because Yunma 4 has a better transfer ability to shoot compared with lu'an.The accumulation of heavy metal of Lu'an mainly focused in root.(4)Pailou soil culture experiments under simulated natural conditions used polluted soil from mine Qixia Mountain which is simulated natural conditions.The results showed that plant growth-promoting bacteria have a positive role in promoting growth of the three hemp cultivars(Yunma 4,lu'an,USO-31).PsJN?Jp3-3 had a better influence(p<0.05)on the growth of hemp seedlings and accumulation of heavy metal while no big difference was found inoculated with J62.Above all,through hydroponic experiments to explore suitable concentration,then using different methods of inoculation at the same cadmium concentration to look for a best application method,then soil culture experiments carried out for further research.The final experiment carried out in the simulated natural conditions to research on the effect caused by PGPB on the growth of hemp and accumulation of heavy metal.We hope that my experiment can provide a reference for the further research of others as well as for the application of hemp. |
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