Root lengths of H. annuus cultivated in the absence or presence of cadmium at various concentrations. Uninoculated seedlings are a control treatment ( ), for the seedlings inoculated with either Micrococcus sp. ( ) or Klebsiella sp. ( ). The error bars are the S.E. of 10 replicates and the small letter above the bar graph denotes a significant difference (p < 0.05) in comparison with the control treatment.