Salicylic Acid Enhanced Low Temperature Stress Tolerance in Vegetables : A Review

Environmental stress such as cold, heat, salinity and drought adversely affect growth and productivity and trigger a series of morphological, physiological, biochemical and molecular changes in plants that eventually interrupt plant life [1, 2]. Most of the arable lands of world, which when exposed to these abiotic stress conditions have an adverse impact on global vegetables production. These abiotic stress conditions decrease crop productivity upto 50-70% [3]. Plants undergo several metabolic cascades for their survival during these stress conditions [4]. Plant’s response is a complex phenotypic and physiological phenomena which is highly influenced by low temperature stress. To enhance the food production, crops are often grown under stressful environments which result in lower yield. The key factors to reduce yield and quality of crops are fluctuations in climatic conditions, such as low temperature stress. During winter season, low temperature stress adversely damages vegetable production. In response to low temperature stress, several phenotypic symptoms such as stunted seedling, poor germination, reduced leaf expansion, yellowing of leaf (Chlorosis) and wilting occur, which sometimes results into tissue damage (necrosis) [5]. Vegetables have an imperative role to play in the diversification of agriculture. They ensure food and nutritional security of the ever budding population of India. However, vegetables are sensitive crops and their production is hindered by various abiotic stresses. Temperature, both low and high, is the most serious environmental stresses. Low temperature stress has been reported as one of the most restraining environmental factors for agricultural crops, particularly vegetables, which accounts for significant crop losses [6]. Summer vegetables are sensitive to chilling temperature (0-15 ◦ C) throughout plant development i.e. seed germination, vegetative growth and reproduction. Under low temperatures, lots of seeds do not germinate or germinate irregularly and plants grow differentially with delayed plant formation leading to variability in crop development. During later stages, plant growth and development are extremely retarded that either limit or lead to no flower and fruit production [7]. Numerous factors affect the degree of injury which may be temperature, time of exposure, organ or tissues of the plant exposed and the physiological stage and temperature at which the plant is being grown [8]. Weak fruit set after a cold period could be due to the poor pollen viability [9]. Chilling sensitivity can occur at two distinct developmental stages i.e., pollen formation (from meiosis to release of mature pollen) and pollen function [10]. Low temperature stress affects the reproductive stages Abstract Low temperature stress adversely affects growth, productivity and triggers a series of morphological, physiological and biochemical changes in plants. It is a major environmental cue that limits the vegetable productivity of plants, particularly in hilly areas. Development of procedures to enhance low temperature stress tolerance in plants is crucial and attracts considerable attention. The tolerance to low temperature stress is an intricate process that involves morphological, physiological and biochemical modifications. Salicylic acid is a vital signalling molecule for modulating plant response to various abiotic stresses. Salicylic acid induced alleviation of low temperature stress has been reported in vegetables. In this review, the aim is to emphasise the ameliorative effects of SA on growth, physiological, biochemical changes, yield and quality of plants growing under low temperature stress. On the basis of different studies, it has been concluded that SA enhanced the low temperature stress tolerance significantly and increased plant growth, photosynthetic pigments, accumulations of osmoprotectants and activity of antioxidant enzymes. It also increased production and quality of vegetables under low temperature stress.