Calcium: A master regulator of stress tolerance in plants

Abstract

The impact of environmental stresses like drought, salinity, extreme temperatures, and high salinity on plants is evident in various physiological, biochemical, and molecular processes. These stressors lead to reduced growth and yield potential. They produce the accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in cells, causing stomatal closure and a decrease in photosynthetic activity. This ultimately results in a loss of crop productivity. Calcium (Ca) serves as a secondary messenger in plants, detected by cellular proteins such as CaM-CAMTAs, CBL1-CIPK, and CDPKs. It plays a crucial role in regulating stress-related genes like RD29A/B and KIN1/2. Calcium is considered a key player in enhancing stress tolerance in plants. Whether applied independently or in conjunction with exogenous plant hormones like salicylic acid, ethylene, abscisic acid, jasmonic acid, and polyamines, it significantly contributes to mitigating abiotic stress. There are various methods to deliver Ca to plants, including seed priming, seed hardening, soil application, and foliar feeding. This review emphasizes the role of Ca, its transportation, sensing mechanisms by cellular proteins (such as CaMs, CBLs, and CDPKs), and the underlying molecular processes in plants under abiotic stress conditions.