Effects of Lead, EDTA, and IAA on Nutrient Uptake by Alfalfa Plants

ABSTRACT

The element concentrations of alfalfa plants exposed for 10 d to 40 mg lead (Pb) L^{− 1} from lead nitrate [Pb(NO₃)₂] alone, or combined with ethylenediaminetetraacetic acid (EDTA) and indole-3-acetic acid (IAA), was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Indole-3-acetic acid at 10 μ M and Pb/EDTA/IAA at 10 μ M increased potassium (K) concentration in roots by 87% and 94%, respectively (P < 0.05). However, IAA at 100 μ M decreased K concentration in leaves (P < 0.05). Plants exposed to 100 μ M IAA, Pb/IAA at 100 μ M, and Pb/EDTA/IAA at 100 μ M had, respectively, 30%, 55%, and 40% more sulfur (S) in leaves than control plants (P < 0.05). Lead and Pb/IAA reduced Ca concentration in stems and leaves (P < 0.05). Conversely, Pb and Pb/EDTA increased Cu concentration in roots and stems. IAA at 100 μ M, Pb, and Pb/EDTA/IAA decreased Zn concentration in roots (P < 0.05). Manganese (Mn) and molybdenum (Mo) concentration in roots and stems was lower in plants treated with Pb and Pb/IAA (P < 0.05). Pb and Pb/IAA reduced (P < 0.05) the iron (Fe) concentration in roots. However, the addition of EDTA and IAA at 10 μ M reduced the negative effects of Pb on Fe absorption.

Keywords::

• Macronutrients
• micronutrients
• lead
• IAA
• EDTA
• phytohormones

ACKNOWLEDGMENTS

The authors acknowledge the National Institutes of Health (grant S06 GM8012-33) and the University of Texas at El Paso's Center for Environmental Resource Management (CERM) through funding from the Office of Exploratory Research of the U.S. Environmental Protection Agency (cooperative agreement CR-819849-01). We also thank the Southwest Consortium for Environmental Research and Policy (SCERP) and the HBCU/MI, Environmental Technology Consortium that is funded by the Department of Energy. Dr. Gardea-Torresdey acknowledges the funding from the National Institute of Environmental Health Sciences (Grant R01ES11367-01) and the Dudley family for the Endowed Research Professorship in Chemistry. Martha L. Lopez also acknowledges the Consejo Nacional de Ciencia y Tecnologia of Mexico (CONACyT) for its financial support (Grant 178763).