Ion Changes and Signaling under Salt Stress in Wheat and Other Important Crops

Abstract

High concentrations of sodium (Na+), chloride (Cl−), calcium (Ca2+), and sulphate (SO42−) are frequently found in saline soils. Crop plants cannot successfully develop and produce because salt stress impairs the uptake of Ca2+, potassium (K+), and water into plant cells. Different intracellular and extracellular ionic concentrations change with salinity, including those of Ca2+, K+, and protons. These cations serve as stress signaling molecules in addition to being essential for ionic homeostasis and nutrition. Maintaining an appropriate K+:Na+ ratio is one crucial plant mechanism for salt tolerance, which is a complicated trait. Another important mechanism is the ability for fast extrusion of Na+ from the cytosol. Ca2+ is established as a ubiquitous secondary messenger, which transmits various stress signals into metabolic alterations that cause adaptive responses. When plants are under stress, the cytosolic-free Ca2+ concentration can rise to 10 times or more from its resting level of 50–100 nanomolar. Reactive oxygen species (ROS) are linked to the Ca2+ alterations and are produced by stress. Depending on the type, frequency, and intensity of the stress, the cytosolic Ca2+ signals oscillate, are transient, or persist for a longer period and exhibit specific “signatures”. Both the influx and efflux of Ca2+ affect the length and amplitude of the signal. According to several reports, under stress Ca2+ alterations can occur not only in the cytoplasm of the cell but also in the cell walls, nucleus, and other cell organelles and the Ca2+ waves propagate through the whole plant. Here, we will focus on how wheat and other important crops absorb Na+, K+, and Cl− when plants are under salt stress, as well as how Ca2+, K+, and pH cause intracellular signaling and homeostasis. Similar mechanisms in the model plant Arabidopsis will also be considered. Knowledge of these processes is important for understanding how plants react to salinity stress and for the development of tolerant crops.

Antioxidant Defense and Ionic Homeostasis Govern Stage-Specific Response of Salinity Stress in Contrasting Rice Varieties

“…Barring S-, T- and S+T+F-stage, CSR36 exhibited significantly low Cl − accumulation in roots and transport low Cl − and high PO 4 3− to the shoots at critical growth stages (F-, S+T- and S+T+F+SS-stages) as compared with Jaya indicating ion selectivity and discrimination ( Figure S4A,B ) [ 40 ]. The low shoot Cl − concentration is maintained by restricting xylem-driven root to shoot transport (i) by higher Cl − efflux from the root to soil solution or (ii) by reducing the xylem loading as evident in CSR36 [ 50 ]. However, SO 4 2− and PO 4 3− are probably assimilated in plant metabolism [ 51 ] resulting enhanced plant growth and reduced internal concentration in roots and shoots as seen in the case of tolerant variety CSR36 under salt stress.…”

Antioxidant Defense and Ionic Homeostasis Govern Stage-Specific Response of Salinity Stress in Contrasting Rice Varieties

“…Barring S-, T-and S+T+F-stage, CSR36 exhibited significantly low Cl − accumulation in roots and transport low Cl − and high PO 4 3− to the shoots at critical growth stages (F-, S+Tand S+T+F+SS-stages) as compared with Jaya indicating ion selectivity and discrimination (Figure S4A,B) [40]. The low shoot Cl − concentration is maintained by restricting xylemdriven root to shoot transport (i) by higher Cl − efflux from the root to soil solution or (ii) by reducing the xylem loading as evident in CSR36 [50]. However, SO 4 2− and PO 4 3− are probably assimilated in plant metabolism [51] resulting enhanced plant growth and reduced internal concentration in roots and shoots as seen in the case of tolerant variety CSR36 under salt stress.…”

Identification of Single Nucleotide Polymorphic Loci and Candidate Genes for Seed Germination Percentage in Okra under Salt and No-Salt Stresses by Genome-Wide Association Study

“…Further statistical analysis of these SNPs revealed that 167 were detected by both programs simultaneously, and they are relatively stable SNP loci (Table S5). These 167 SNPs were located on 21 of the 65 okra chromosomes, namely, chromosomes 4,5,15,17,19,22,24,25,31,37,40,41,43,44,45,46,54,56,59, 61, and 64. Among them, chromosome 31 had the most marker-trait associations (66) detected.…”

“…Soil salinization is an important environmental factor that affects germination, growth and development, and yield. Soil salinization poses a serious threat to global crop production [ 5 ].…”