Nickel and Zinc Isotope Fractionation in Hyperaccumulating and Nonaccumulating Plants

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• 作者：Teng-Hao-Bo Deng ; Christophe Cloquet ; Ye-Tao Tang ; Thibault Sterckeman ; Guillaume Echevarria ; Nicolas Estrade ; Jean-Louis Morel ; Rong-Liang Qiu
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：October 21, 2014
• 年：2014
• 卷：48
• 期：20
• 页码：11926-11933
• 全文大小：339K
• ISSN：1520-5851

文摘

Until now, there has been little data on the isotope fractionation of nickel (Ni) in higher plants and how this can be affected by plant Ni and zinc (Zn) homeostasis. A hydroponic cultivation was conducted to investigate the isotope fractionation of Ni and Zn during plant uptake and translocation processes. The nonaccumulator Thlaspi arvense, the Ni hyperaccumulator Alyssum murale and the Ni and Zn hyperaccumulator Noccaea caerulescens were grown in low (2 渭M) and high (50 渭M) Ni and Zn solutions. Results showed that plants were inclined to absorb light Ni isotopes, presumably due to the functioning of low-affinity transport systems across root cell membrane. The Ni isotope fractionation between plant and solution was greater in the hyperaccumulators grown in low Zn treatments (螖⁶⁰Ni_{plant-solution} = 鈭?.90 to 鈭?.63鈥? than that in the nonaccumulator T. arvense (螖⁶⁰Ni_{plant-solution} = 鈭?.21鈥?, thus indicating a greater permeability of the low-affinity transport system in hyperaccumulators. Light isotope enrichment of Zn was observed in most of the plants (螖⁶⁶Zn_{plant-solution} = 鈭?.23 to 鈭?.10鈥?, but to a lesser extent than for Ni. The rapid uptake of Zn on the root surfaces caused concentration gradients, which induced ion diffusion in the rhizosphere and could result in light Zn isotope enrichment in the hyperaccumulator N. caerulescens. In high Zn treatment, Zn could compete with Ni during the uptake process, which reduced Ni concentration in plants and decreased the extent of Ni isotope fractionation (螖⁶⁰Ni_{plant-solution} = 鈭?.11 to 鈭?.07鈥?, indicating that plants might take up Ni through a low-affinity transport system of Zn. We propose that isotope composition analysis for transition elements could become an empirical tool to study plant physiological processes.