Sodium Influx and Potassium Efflux Currents in Sunflower Root Cells Under High Salinity

Abstract

Helianthus annuus L. is an important oilseed crop, which exhibits moderate salt tolerance and can be cultivated in areas affected by salinity. Using patch-clamp electrophysiology, we have characterized Na+ influx and K+ efflux conductances in protoplasts of salt-tolerant H. annuus L. hybrid KBSH-53 under high salinity. This work demonstrates that the plasma membrane of sunflower root cells has a classic set of ionic conductances dominated by K+ outwardly rectifying channels (KORs) and non-selective cation channels (NSCCs). KORs in sunflower show extreme Na+ sensitivity at high extracellular [Ca2+] that can potentially have a positive adaptive effect under salt stress (decreasing K+ loss). Na+ influx currents in sunflower roots demonstrate voltage-independent activation, lack time-dependent component, and are sensitive to Gd3+. Sunflower Na+-permeable NSCCs mediate a much weaker Na+ influx currents on the background of physiological levels of Ca2+ as compared to other species. This suggests that sunflower NSCCs have greater Ca2+ sensitivity. The responses of Na+ influx to Ca2+ correlates well with protection of sunflower growth by external Ca2+ in seedlings treated with NaCl. It can be, thus, hypothesized that NaCl tolerance in sunflower seedling roots is programmed at the ion channel level via their sensitivity to Ca2+ and Na+.

Green-Synthesized Nanocellulose Enhanced Germination, Morphology Roots, Nutrients Influx of Wheat Seedlings under Salinity Stress

“…Interestingly, the response of Na+ influx to Ca2+ induced protection of root growth in wheat seedlings treated with NC. The results agree with Hryvusevich et al (2021).…”

“…This may be due to high content of Ca 2+ ions in NC. Hryvusevich et al (2021) reported that Ca 2+ ions are blockers of plant Na+-permeable NSCCs However, the decrease of external Ca2+ resulted in the increase in the inward Na+ current. Interestingly, the response of Na+ influx to Ca2+ induced protection of root growth in wheat seedlings treated with NC.…”

Silicon Induces Heat and Salinity Tolerance in Wheat by Increasing Antioxidant Activities, Photosynthetic Activity, Nutrient Homeostasis, and Osmo-Protectant Synthesis

“…We noted that the accumulation of Na + and Cl − was significantly increased under combined heat and saline conditions ( Figure 5 and 6), while the uptake of K + was significantly decreased under HS and SS, which could be due to an increase in K + efflux [ 87 ]. However, this mechanism remains to be confirmed, although this efflux of K + can be reduced via the application of osmo-protectants and nutrients application [ 88 ].…”

Foliar Application of Ascorbic Acid and Tocopherol in Conferring Salt Tolerance in Rapeseed by Enhancing K+/Na+ Homeostasis, Osmoregulation, Antioxidant Defense, and Glyoxalase System

“…Severe salinity stress enhances Na + influx through the non-selective cation channels of the plasma membrane, and this triggers potassium ion (K + ) efflux, resulting in an elevated Na + /K + ratio in plant cells [4]. The resulting ion imbalance causes nutrient deficiency, especially K + deficiency, which then alters stomatal regulation, reduces leaf area, induces leaf senescence and premature abscission, and destroys photosynthetic capability, resulting in drastic declines in yield and yield-contributing components in crops [5][6][7].…”