Organic acids enhance the uptake of lead by wheat roots |
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Authors: | Huanhua Wang Xiaoquan Shan Tao Liu Yaning Xie Bei Wen Shuzhen Zhang Fang Han Martinus Th. van Genuchten |
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Affiliation: | (1) State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P. O. Box 2871, Beijing, 100085, China;(2) Beijing Synchrotron Radiation Laboratory, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China;(3) U.S. Salinity Laboratory, USDA-ARS, 450 West Big Springs Road, Riverside, CA 92501, USA |
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Abstract: | The uptake and bioavailability of lead (Pb) in soil–plant systems remain poorly understood. This study indicates that acetic and malic acids enhance the uptake of Pb by wheat (Triticum aestivum L.) roots under hydroponic conditions. The net concentration-dependent uptake influx of Pb in the presence and absence of organic acids was characterized by Michaelis–Menten type nonsaturating kinetic curves that could be resolved into linear and saturable components. Fitted maximum uptake rates (V max) of the Michaelis–Menton saturable component in the presence of acetic and malic acids were, respectively, 2.45 and 1.63 times those of the control, while the Michaelis–Menten K m values of 5.5, 3.7 and 2.2 μM, respectively, remained unchanged. Enhanced Pb uptake by organic acids was partially mediated by Ca2+ and K+ channels, and also depended upon the physiological function of the plasma membrane P-type ATPase. Uptake may have been further enhanced by an effectively thinner unstirred layer of Pb adjacent to the roots, leading to more rapid diffusion towards roots. X-ray absorption spectroscopic studies provided evidence that the coordination environment of Pb in wheat roots was similar to that of Pb(CH3COO)2·3H2O in that one Pb atom was coordinated to four oxygen atoms via the carboxylate group. |
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Keywords: | Ca2 + and K+ channels Organic acids P-type ATPase Uptake of lead (Pb) Wheat (Triticum aestivum L.) X-ray absorption spectroscopy |
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