Calcium-mediated signaling mechanisms enhancing drought tolerance and agronomic resilience in arable crops.

Despite major advances in identifying calcium (Ca2+) signaling components involved in drought-tolerant crops, key challenges remain regarding how Ca2+ signaling interacts with abscisic acid (ABA), reactive oxygen species (ROS), and ion-transport networks. This review synthesized evidence from studies published between 1998 and 2026 on Ca2+-mediated drought tolerance mechanisms in arable crops. Evidence was evaluated from studies on membrane stability and ABA responses to multi-omics investigations of kinase regulation and stress-signaling integration. Studies included cereal (maize, rice, wheat), fiber (cotton), oilseed (canola), legume (faba bean), and horticultural (tomato) crops, with maize and rice being the most extensively studied species. The synthesis identified Ca2+ signaling as a key regulator of drought adaptation, driven predominantly by kinase-mediated pathways, with more limited evidence linking Ca2+/calmodulin signaling and ion-channel regulation to coordinated physiological processes. Drought-tolerance mechanisms included ABA-mediated stomatal closure, ion transport regulation, ROS detoxification, antioxidant activation, osmotic adaptation, and stress-responsive gene expression. ABA-mediated stomatal regulation was the most consistently supported mechanism, ROS-linked responses showed association without clear causality, and ion-channel regulation and stress-memory responses remain underexplored. These processes may contribute to improved water-use efficiency, antioxidant protection, membrane stability, and yield maintenance under drought conditions. In addition, agronomic practices that enhance calcium availability may support drought resilience under field conditions, though the underlying molecular link remains unproven. Thus, integrated management strategies, including soil amendments, foliar sprays, and irrigation, may help improve drought tolerance in crops. Future research should emphasize genome editing, multi-omics integration, field validation, and molecular breeding to develop climate-resilient crop cultivars.