Raddatz Natalia, Morales de Los Ríos Laura, Lindahl Marika, Quintero Francisco J, Pardo José M
Institute of Plant Biochemistry and Photosynthesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Seville, Spain.
Front Plant Sci. 2020 Mar 6;11:247. doi: 10.3389/fpls.2020.00247. eCollection 2020.
Potassium (K) and nitrogen (N) are essential nutrients, and their absorption and distribution within the plant must be coordinated for optimal growth and development. Potassium is involved in charge balance of inorganic and organic anions and macromolecules, control of membrane electrical potential, pH homeostasis and the regulation of cell osmotic pressure, whereas nitrogen is an essential component of amino acids, proteins, and nucleic acids. Nitrate (NO ) is often the primary nitrogen source, but it also serves as a signaling molecule to the plant. Nitrate regulates root architecture, stimulates shoot growth, delays flowering, regulates abscisic acid-independent stomata opening, and relieves seed dormancy. Plants can sense K/NO levels in soils and adjust accordingly the uptake and root-to-shoot transport to balance the distribution of these ions between organs. On the other hand, in small amounts sodium (Na) is categorized as a "beneficial element" for plants, mainly as a "cheap" osmolyte. However, at high concentrations in the soil, Na can inhibit various physiological processes impairing plant growth. Hence, plants have developed specific mechanisms to transport, sense, and respond to a variety of Na conditions. Sodium is taken up by many K transporters, and a large proportion of Na ions accumulated in shoots appear to be loaded into the xylem by systems that show nitrate dependence. Thus, an adequate supply of mineral nutrients is paramount to reduce the noxious effects of salts and to sustain crop productivity under salt stress. In this review, we will focus on recent research unraveling the mechanisms that coordinate the K-NO ; Na-NO , and K-Na transports, and the regulators controlling their uptake and allocation.
钾（K）和氮（N）是必需营养素，它们在植物体内的吸收和分布必须相互协调，以实现最佳生长和发育。钾参与无机和有机阴离子及大分子的电荷平衡、膜电位控制、pH稳态以及细胞渗透压调节，而氮是氨基酸、蛋白质和核酸的重要组成部分。硝酸盐（NO₃⁻）通常是主要的氮源，但它也是植物的信号分子。硝酸盐调节根系结构、刺激地上部生长、延迟开花、调节不依赖脱落酸的气孔开放并解除种子休眠。植物能够感知土壤中的钾/硝酸盐水平，并相应地调整吸收和根茎运输，以平衡这些离子在器官间的分布。另一方面，少量的钠（Na）被归类为植物的“有益元素”，主要作为一种“廉价”的渗透剂。然而，当土壤中钠浓度过高时，它会抑制各种生理过程，损害植物生长。因此，植物已经形成了特定机制来运输、感知和响应各种钠环境。许多钾转运蛋白也能吸收钠，并且地上部积累的大部分钠离子似乎是通过依赖硝酸盐的系统装载到木质部中的。因此，充足的矿质营养供应对于减轻盐分的有害影响以及在盐胁迫下维持作物生产力至关重要。在本综述中，我们将重点关注最近的研究，这些研究揭示了协调钾-硝酸盐、钠-硝酸盐和钾-钠运输的机制，以及控制它们吸收和分配的调节因子。
