Salicylic acid (SA) chemically known as 2-hydroxy benzoic acid, is a ubiquitous endogenous plant growth regulator of phenolic nature, synthesized by plants which acts as a vital endogenous signaling molecule in plant immune response. SA is recognized as a multifaceted element that have crucial roles in various plant physiological processes such as seed germination, seedling growth, photosynthetic activity, nutrient absorption and transport, respiration, nitrogen metabolism, thermogenesis, stomatal closure, flowering, expression of senescence-related genes, inducing antioxidant defense system and resistance to a broad spectrum of pathogens. SA mode of action varies with plant species, plant developmental phase, its mode of application, and its endogenous level in the plant. SA have high metabolic and physiological activity therefore, involved in the activation of plant defense responses against biotic and abiotic stress factors and also involved in the transcriptional reprograming and in controlling transcription and expression of several defense related genes. SA in minor quantities provide plant stress tolerance, but high amounts of SA triggers oxidative stress due to generation of plethora of ROS which ultimately lead to cell death. Under stress conditions, SA interplays with reactive oxygen species (ROS) as crucial signaling molecules for inducing genetically controlled defense-related mechanisms and expression of genes that cause defense against stress. Keeping these points in mind, various aspects like significance of SA for plants, its stress mitigation properties as well as cross-talk with other plant growth regulators have been mentioned. The book has seven chapters which deal with the role of phytohormone salicylic acid in plants, its mechanism of synthesis, signaling & homeostasis in plants, its crosstalk with ROS in mitigation of stress and its interaction with other plant growth regulators. We believe that this book comprises a wealth of knowledge to botanists, agriculturists, students and researchers of colleges and universities.
