Effects of metal resistant plant growth promoting bacteria on corn growth and Zn accumulation

Objective Effects of metal resistant plant growth promoting bacteria(PGPB) on corn growth and Zn accumulation were studied to provide a fundamental groundwork for mitigating the stress of heavy metal on crop growth and decreasing heavy metal uptake.

Method A pot experiment was carried out to study the effects of inoculation with two Zn resistant PGPB, Ⅱ₂R₃ and Ⅳ₈R₃ on corn plant growth and Zn uptake from Zn contaminated soils (0, 200, 400 and 800 mg·kg^-1 Zn addition).

Result and conclusion The strains Ⅱ₂R₃ and Ⅳ₈R₃ not only grew well with different concentrations of Zn, but also absorbed or accumulated much higher Zn from the growing medium. Individual inoculation of strain Ⅳ₈R₃ to the soil with 200 or 400 mg·kg^-1 Zn addition both promoted the corn growth. For the soils with 800 mg·kg^-1Zn addition, simultaneous inoculation with strains Ⅱ₂R₃ and Ⅳ₈R₃ promoted the corn growth. Individual or simultaneous inoculation with strains Ⅱ₂R₃ and Ⅳ₈R₃ to the soils at three Zn pollution levels (200, 400 and 800 mg·kg^-1 Zn addition) decreased the soil bioavailable Zn concentration. For the soil with a high Zn pollution level (800 mg·kg^-1Zn addition), the inoculation of strains Ⅱ₂R₃ orⅡ₂R₃+Ⅳ₈R₃ decreased Zn uptake and transportation in corn. However, all of three inoculation treatments had no significant effects on Zn uptake of corn when strains Ⅱ₂R₃, Ⅳ₈R₃, Ⅱ₂R₃+Ⅳ₈R₃ were inoculated to the soils with 200 or 400 mg·kg^-1 Zn addition. The results indicate that inoculation with metal resistant PGPB to high Zn-contaminated soil can promote the corn growth and inhibite the uptake and transportation of Zn in corn. Inoculation with strains Ⅱ₂R₃ or Ⅳ₈R₃ to high Zn-contaminated soils can inhibite the uptake and transportation of Zn in corn. The effects of inoculation with strains Ⅱ₂R₃ or Ⅳ₈R₃ on corn growth are related to the different levels of Zn pollution and characterization of the strains.