Henriksen G H, Bloom A J, Spanswick R M
Section of Plant Biology, Division of Biological Sciences, Cornell University, Ithaca, New York 14853.
Plant Physiol. 1990 May;93(1):271-80. doi: 10.1104/pp.93.1.271.
Neutral carrier-based liquid membrane ion-selective microelectrodes for NH(4) (+) and NO(3) (-) were developed and used to investigate inorganic nitrogen acquisition in two varieties of barley, Hordeum vulgare L. cv Olli and H. vulgare L. cv Prato, originating in cold and warm climates, respectively. In the present paper, the methods used in the fabrication of ammonium- and nitrate-selective microelectrodes are described, and their application in the study of inorganic nitrogen uptake is demonstrated. Net ionic fluxes of NH(4) (+) and NO(3) (-) were measured in the unstirred layer of solution immediately external to the root surface. The preference for the uptake of a particular ionic form was examined by measuring the net flux of the predominant form of inorganic nitrogen, with and without the alternative ion in solution. Net flux of NH(4) (+) into the cold-adapted variety remained unchanged when equimolar concentrations (200 micromolar) of NH(4) (+) and NO(3) (-) were present. Similarly, net flux of NO(3) (-) into the warm-adapted variety was not affected when NH(4) (+) was also present in solution. The high temporal and spatial resolution afforded by ammonium- and nitrate-selective microelectrodes permits a detailed examination of inorganic nitrogen acquisition and its component ionic interactions.
开发了基于中性载体的用于铵离子（NH₄⁺）和硝酸根离子（NO₃⁻）的液膜离子选择性微电极，并用于研究分别起源于寒冷和温暖气候的两个大麦品种（大麦属普通大麦品种奥利和普通大麦品种普拉托）对无机氮的吸收。本文描述了铵离子和硝酸根离子选择性微电极的制备方法，并展示了它们在无机氮吸收研究中的应用。在根表面紧邻的未搅拌溶液层中测量了NH₄⁺和NO₃⁻的净离子通量。通过测量无机氮主要形式的净通量，在溶液中有和没有替代离子的情况下，研究了对特定离子形式吸收的偏好。当存在等摩尔浓度（200微摩尔）的NH₄⁺和NO₃⁻时，NH₄⁺向冷适应品种的净通量保持不变。同样，当溶液中也存在NH₄⁺时，NO₃⁻向暖适应品种的净通量不受影响。铵离子和硝酸根离子选择性微电极提供的高时空分辨率允许对无机氮吸收及其组成离子相互作用进行详细研究。
