Coordinated Transport of Nitrate, Potassium, and Sodium

Abstract

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 3 − ) 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 3 − 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 3 − ; Na + -NO 3 − , and K + -Na + transports, and the regulators controlling their uptake and allocation.

Germination and Growth of Spinach under Potassium Deficiency and Irrigation with High-Salinity Water

“…Eggplant varieties subjected to increasing salinity during germination and seedling stages also responded differently depending on plant growth stage, with salinity tolerance of all cultivars increasing at the later growth stages [ 36 ]. Spinach plants, even under very low levels of K maintained optimal plant growth, suggesting that there are genetic mechanisms that are triggered under either low K, or both low K and high salinity, that are responsible for K and N, and maybe P, homeostasis in the plant as previously discussed [ 8 , 52 , 53 ]. Our results suggest that spinach plants can tolerate moderate to high salinity in sandy soils, and when applied a leaching fraction of approximately 0.30, having the ability to adjust to some degree of salinity as plants grow older.…”

Comprehensive dissection into morpho-physiologic responses, ionomic homeostasis, and transcriptomic profiling reveals the systematic resistance of allotetraploid rapeseed to salinity

“…Soil salinity inhibits crop growth and development, which in turn reduces yield production, through a two-phase physiological dysfunction: (i) osmotic stresses that declines water potential and (ii) ion toxicity that disturbs ion homeostasis [ 6 ]. These stresses are associated with the disorder of a variety of biological processes, including cellular homeostasis imbalance, oxidative stress, essential nutrient dysfunction, protein synthesis disruption, retarded organ growth, and even plant death [ 7 ].…”

Transcriptome Analysis Unravels Key Factors Involved in Response to Potassium Deficiency and Feedback Regulation of K+ Uptake in Cotton Roots

“…Transcription factors (TFs) may act as molecular switches to regulate clusters of gene expression in response to stress in higher plants [ 78 ]. It has been known that the Phosphate starvation response 1 (PHR1) is the key TF in Pi starvation; it coordinates with other MYBs and WRKYs to up- or down-regulate a subset of Pi starvation-induced ( PSI) genes in response to Pi deficiency [ 79 ]. In addition, there is a key TF, NIN-like 7 protein (NLP7), and a series of other TFs implicated in the control of genes related to NO 3 − transport and metabolism under low NO 3 − conditions [ 80 ].…”