Salicylic Acid a Multifaceted Hormone for Vegetable Crops- A Review SUNIL PRAJAPATI 1* , SANT KUMAR SHARMA 2 AND SATISH KADWEY 3 1 Department of Horticulture (Vegetable Science), Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur, 482004 (Madhya Pradesh) 2 Mahatma Gandhi Chitrakoot Gramodaya Vishwa Vidyalaya, Chitrakoot, Satna (M.P.) 3 (TMC-Project) Krishi Vigyan Kendra, Chhindwara (M.P.) India. *email: prajapatisunil4960@gmail.com ABSTRACT In recent years salicylic acid has been the focused of intensive research due to its function as an endogenous signal mediating and systemic plant defence responses against pathogens. It has also been found that SA plays a role during the plant response to abiotic stresses such as drought, chilling, heavy metal toxicity, heat, and osmotic stress. In this sense, SA appears to be, just an ‘effective therapeutic agent’ for plants, SA play a crucial role in the regulation of physiological and biochemical processes during entire lifespan of the plant. Salicylic acid, a naturally occurring plant hormone acting as a important signaling molecule. It plays a vital role in plant growth, ion uptake and transport. Salicylic acid is also involved in endogenous signaling to trigger plant defense against pathogens. This positive effect of SA could be attributed to an increased CO 2 assimilation and photosynthetic rate and increased mineral uptake by the stressed plant under Salicylic acid treatment. The application of salicylic acid, acetylsalicylic acid or other analogues of Salicylic acid, to leaves of corn and soybean accelerated their leaf area and dry mass production, but plant height and root length remained unaffected. SA reduced the Na uptake of plants or increased the uptake of N, P, K, Ca, Mg and the other minerals as compared to control treatment under salt stress. The environment is greatly affected by climatic changes resulting in both biotic and abiotic stresses. Stresses occurring at the primary and secondary levels lead to abiotic stresses that consequently affect the yield of crop plants. Key words Salicylic acid, growth, yield, post harvest, biotic and abiotic resistance. Salicylic acid belongs to group of chemicals known as phenolic is considered as a plant “aspirin” in acetylated form. Salicylic Acid, a white crystalline solid that is used chiefly in the preparation of aspirin and other pharmaceutical products, the free acid occurs naturally in small amounts in many plants, particularly the various species of Spiraea. SA known to affect various physiological and biochemical activities of plants and play a key role in regulating their growth and productivity (Hayat, et al., 2010). Salicylic acid is considered to be an endogenous growth regulator of phenolic nature that enhanced the leaf area and dry mass production (Khan, et al., 2003).It also regulates number of processes including thermo genesis, the defence response to pathogen attack, ethylene synthesis and fruit ripening. It has the role of regulating plant responses to some a biotic stresses particularly to UV radiation and ozone. It plays a key role in signal transduction pathway leading to systemic acquired resistance against a broad spectrum of pathogens. Exogenous application of salicylic acid at non-toxic concentrations to susceptible plans could enhance resistance to pathogens (Murphy, et al., 1998). The methyl ester also occurs widely in nature; it is the chief constituent of oil of wintergreen. Salicylic acid is endogenous signal molecules, playing vital roles in regulating stress responses and plant developmental processes including heat production or thermo genesis, photosynthesis, stomata conductance, transpiration, ion uptake and transport, disease resistance, seed germination, sex polarization, glycolysis and crop yield and. Currently, salicylic acid has received a particular attention because it is a key signal molecule for expression of multiple modes of plant stress resistance. Although the focus has been mainly on the roles of salicylic acid on biotic stresses, several studies also support major roles of salicylates in modulation of the plant response to several abiotic stresses, such as UV light, drought, salinity, chilling stress and heat shock. Salicylates delay the ripening of fruits, probably through inhibition of ethylene biosynthesis or action, and maintain post-harvest quality. Multifaceted of Salicylic acid in plants  Salicylic acid as plant hormone at present it is in gradually adaptation.  Exogenous application of salicylic acid reduces storage rots in a number of Trends in Biosciences 8(5), Print : ISSN 0974-8, 1179-1185, 2015