Selection Of Cadmium-, Arsenic-, Plumbum-tolerant Plant Growth-promoting Bacteria And Regulation Of Plant Growth-promoting Bacteria On Sorghum Bicolor(L.)Moench Growth

Sweet sorghum is considered as one of high biomass and high value energy plant, while energy plants grown in heavy metal contaminated soil will definitely be stressed by heavy mental. This research selected plant growth promoting bacteria (PGPB) from the plant roots and their rhizosphere soils which were contaminated by heavy metals. The regulation of PGPB on growth of sweet sorghum seedlings under mainly Cd contaminated soil was discussed in this paper. The main results were as follows.Plants and their rhizosphere soil samples were collected from heavy mental contaminated area in Changsha, Hunan. Nine bacterial strains which can survive in LB plate medium culture containing Cd, Pb, As. Among all bacteria obtained, FWJ1、FWJ2、 BH1、QC、NF2、WJ1presented various degrees of tolerances to Cd、Pb、As. The strains PPN2, LC, QGC2showed tolerance to Pb、As. The endophyte strains BH1, QGC1, FWJ1, WJ1and LC were isolated from Menthae Folium, Sagina japonica (Sw.) Ohwi, Pteris vittata, Caulis et Folium Lactucae sativae and Humulus scandens (Lour.) Merr, respectively, while the rhizosphere strains QC, NF2, PPN2and FWJ2were separately isolated from rhizosphere soil of Apium graveolens L, Malachium aquaticum (L.) Fries, Veronica persica Poir and Pteris vittata. The strains FWJ1, FWJ2, QC, NF2, WJ1, PPN2, LC and QGC2belong to Bacillus subtilis, while BH1belongs to Chryseobacterium sp.The shoot and root biomass of sweet sorghum seedlings, chlorophyll contents decreased with the Cd concentration increasing under hydroponic culture. However, the contents of Cd in plant seedlings increased significantly with the increasing Cd exposed concentration (p<0.05)The effects of spraying PGPB on plants soil cultured had been researched in this experiment. The results showed that spraying WJ1and FWJ1eased the stress of growth of sweet sorghum seedlings under the treatment of50mgkg-1Cd. The fresh weights of shoot and root of sweet sorghum seedlings, water contents and Cd absorption were increased compared with the control. Among these, WJ1and FWJ1promoted biomass while WJ1obviously enhanced chlorophyll contents (p<0.05)The effects of the various strains, such as FWJ2, LC, NF2, QC, PPN2, QGC, BH1on sweet sorghum growth had been studies using NAU campus soil and Zhuzhou heavy metal contaminated soil. The fresh weights of shoot and root of sweet sorghum seedlings planted in the NAU campus soil were dramatically higher than those under the heavy metal contaminated soil from Zhuzhou. The contents of Zn, Cd and Cu in soil from Zhuzhou were30.7,8.6and6.0times as high as that of campus soil, respectively. The results showed that the shoot and root growth, photosynthetic parameters under PGPB treatment increased significantly compared with the controls for two soil conditions. And degree of PGPB improving growth of sweet sorghum seedlings in non-contaminated soil was more obvious. From all of the results demonstrated above, there was great potential to regulate C4-high biomass energy plant by using PGPB separated from heavy mental contaminated soil or rhizosphere soil. Its regulation mechanism needs to be further studied.