From Individual to Combined Stress: Cadmium and Salinity Tolerance in Lentil and the Potential of PGRs Foliar Interventions

Abstract.

Salinity and cadmium toxicity are among the major abiotic stress that restrict plant growth and productivity through disturbances in water relations, ion homeostasis, nutrient acquisition, photosynthesis and cellular metabolism. Salinity imposes both osmotic and ionic constraints, whereas Cd is non-essential and potentially toxic metal that can interfere with physiological processes and induce oxidative stress. The simultaneous occurrence of salinity and Cd may intensify these effects because alterations in soil and plant ion relations can influence Cd availability uptake and biochemical functions. Plants naturally activate antioxidant, osmotic and metabolic defense mechanisms to limit stress-induced injury, however these responses may not always be sufficient under severe stress conditions. Foliar applications of plant growth regulators (PGRs) have therefore gained considerable attention as an approach for enhancing plant tolerance. Ascorbic acid (AsA) contributes to cellular redox regulation and reactive oxygen species (ROS) detoxification. Riboflavin (RIBO) supports redox metabolism and stress-responsive processes. Thiourea (TU) through its sulfur-containing functional group and regulatory effects on antioxidant metabolism, can strengthen plant defense under adverse conditions. Proline functions as an osmoprotectant and contributes to osmotic adjustment, membrane and protein protection and ROS regulation. Salicylic acid (SA) an important signaling molecule that regulates antioxidant defense associated with stress adaptation. This review examines the individual and combined effects of salinity and Cd toxicity on lentil and the protective role of PGRs in alleviating stress-induced damage. Lentil (Lens culinaris Medik.) is an important pulse crop with substantial nutritional and agricultural value and is sensitive to salinity and heavy metal stress. Understanding the interactions among combined salinity-Cd stress, lentil defense mechanisms and foliar applications protective compounds may provide a useful basis for improving lentil performance and productivity under multiple environmental constraints.