Plant Growth‐Promoting Bacteria Promote Copper and Iron Translocation from Root to Shoot in Alfalfa Seedlings

Abstract

Plant growth‐promoting microorganisms have been utilized to promote plant potentialities and it has been reported that some bacterial strains can help certain plants to acquire iron (Fe) via siderophores. In this investigation it has been demonstrated that certain bacterial strains that synthesize siderophores influence copper (Cu) and Fe accumulation in alfalfa (Medicago sativa) seedlings mainly because they are able to modulate metal translocation from root to shoot. The roots of inoculated seedlings, growing in a solution containing 10 mg L⁻¹ of CuSO₄·5H₂O plus 10 mg L⁻¹ of FeCl₃·6H₂O, accumulated in a period of 8 days from 97 (UAP154 and UAP40) to 120 (U) mg of Cu per kg of dry matter (mean 110.41) and Fe from 126 (UAP154 and UAP40) to 151 (U, Avm, and CPMex46) (mean 139.26) while the non‐inoculated ones accumulated 103.8 and 146.9 mg of Cu and Fe per kg of dry mass, respectively. The accumulated Cu in stems of seedlings inoculated with the strains CPMex46, Avm, and UAP154 was 33, 24, and 0.3% more than the amount of Cu accumulated in stems of non‐inoculated seedlings (33.7 mg of metal per kg of dry mass). In the case of Fe, the stems of seedlings inoculated with the strains Avm, CPMex46, UAP40, and UAP154 accumulated 37, 31, 4, and 2% more Fe, respectively, as compared with the non‐inoculated seedlings (78.8 mg of metal per kg of dry mass). These results demonstrate that the strains CPMex46 and Avm improve both Cu and Fe translocation potential from root to shoot in alfalfa seedlings, fact that may be consider to promote the use of alfalfa crop for bioremediation applications.

Keywords:

• Metal uptake
• Metal accumulation
• Bioremediation

Acknowledgments

The authors acknowledge financial support from the Center for Environmental Resource Management (CERM) at the University of Texas at El Paso through funding from the Office of Exploratory Research of the US EPA (Cooperative Agreement CR‐819849‐01‐04). Dr. Gardea‐Torresdey would also like to acknowledge the financial support of the National Institutes of Health (Grant SO6 GM8012‐30).