Figure 2.

The effect of root exudates on the phosphate-solubilizing ability of B. frigoritolerans (A) and the nitrogen-fixation of B. megaterium (B) and their densities (C). C₀, sterile water; C₁, 20×the volume of concentrated root exudates; C₂, 40×the volume of concentrated root exudates; C₃, 60×the volume of concentrated root exudates. Different lowercase letters above the data bar indicate that the strain with different concentrations root exudates has significant differences at the p < 0.05 level. The “*”indicated that density of the Bacillus strains multiplied by 10⁶.