Salt stress alleviation in peanut through calcium supplementation

Abstract

Peanut, being moderately salt sensitive, requires efficient management strategies to endure salt stress. A pot experiment was envisaged to evaluate the effect of exogenous calcium chloride (CaCl₂) on the underlying physiological and biochemical mechanisms in peanut during salinity stress. Salinity-induced membrane destabilization significantly increased thiobarbituric acid reactive substances (TBARS) and H₂O₂ (hydrogen peroxide) accumulation with susceptible cultivars (TG 37A and GJG 31) experiencing greater oxidative stress. There was a significant reduction in leaf stomatal conductance and net photosynthetic rate (P_N), concomitant with the decrease in shoot and root potassium (K⁺) and shoot calcium (Ca²⁺) concentrations due to greater accumulation of sodium (Na⁺). The salt stress alleviating potential of calcium was exhibited by a significant increase in shoot K⁺/ Na⁺ ratio along with elevated Ca²⁺ concentrations, which aided in restricting Na⁺ accumulation in roots and shoots of calcium-treated, salt-stressed cultivars. This ionic homeostasis was accompanied with a significant increase in membrane stability index with reduced TBARS and H₂O₂ accumulation, ROS detoxification through elevated total antioxidant activity and increased osmoregulatory compounds such as proline, total phenols and soluble sugars in calcium-treated salt-stressed plants compared to control. The improved pigment retention, stomatal conductance and ionic balance contributed to a significant increase in P_N, which was also reflected in the improved yield attributes of the peanut cultivars. Thus, the foliar application of CaCl₂ offers a promising approach to alleviate the adverse impact of salt stress in peanut, particularly at 4 dSm⁻¹, which otherwise imposes severe yield losses in the crop.