Salicylic acid (SA) is a plant phytohormone that plays a crucial role in plant growth and development beyond its well-known function in defense against pathogens. SA is involved in regulating physiological and biochemical processes throughout the plant's life cycle, including seed germination, vegetative growth, photosynthesis, respiration, thermogenesis, flower formation, seed production, senescence, and programmed cell death. It also contributes to maintaining cellular redox homeostasis by regulating antioxidant enzymes and inducing alternative respiratory pathways. SA can enhance seed germination under abiotic stress conditions by reducing oxidative damage and promoting protein synthesis essential for germination. It also influences photosynthesis by modulating leaf and chloroplast structure, stomatal closure, and chlorophyll content. SA helps protect plants against oxidative stress by reducing reactive oxygen species (ROS) levels, which is crucial for maintaining photosynthetic efficiency. Additionally, SA is involved in light acclimation by regulating redox homeostasis and interacting with other signaling pathways, such as those involving ethylene, jasmonic acid, and abscisic acid. SA also plays a role in stomatal closure, which is important for photosynthesis and plant defense. In terms of growth, SA affects plant development by regulating cell division, growth rate, and the balance between photosynthesis and growth. It interacts with other phytohormones, such as auxins and gibberellins, and is involved in the regulation of flowering by interacting with photoperiod and autonomous pathways. SA is also involved in senescence regulation by modulating gene expression and influencing the balance of ROS levels. Overall, SA is a key regulator of plant growth and development, with complex interactions with other signaling pathways and phytohormones.Salicylic acid (SA) is a plant phytohormone that plays a crucial role in plant growth and development beyond its well-known function in defense against pathogens. SA is involved in regulating physiological and biochemical processes throughout the plant's life cycle, including seed germination, vegetative growth, photosynthesis, respiration, thermogenesis, flower formation, seed production, senescence, and programmed cell death. It also contributes to maintaining cellular redox homeostasis by regulating antioxidant enzymes and inducing alternative respiratory pathways. SA can enhance seed germination under abiotic stress conditions by reducing oxidative damage and promoting protein synthesis essential for germination. It also influences photosynthesis by modulating leaf and chloroplast structure, stomatal closure, and chlorophyll content. SA helps protect plants against oxidative stress by reducing reactive oxygen species (ROS) levels, which is crucial for maintaining photosynthetic efficiency. Additionally, SA is involved in light acclimation by regulating redox homeostasis and interacting with other signaling pathways, such as those involving ethylene, jasmonic acid, and abscisic acid. SA also plays a role in stomatal closure, which is important for photosynthesis and plant defense. In terms of growth, SA affects plant development by regulating cell division, growth rate, and the balance between photosynthesis and growth. It interacts with other phytohormones, such as auxins and gibberellins, and is involved in the regulation of flowering by interacting with photoperiod and autonomous pathways. SA is also involved in senescence regulation by modulating gene expression and influencing the balance of ROS levels. Overall, SA is a key regulator of plant growth and development, with complex interactions with other signaling pathways and phytohormones.