Temperature sensitivity of food legumes: a physiological insight
Of the various environmental stresses that a plant can experience, temperature has the widest and most far-reaching effects on legumes. Temperature extremes, both high (heat stress) and low (cold stress), are injurious to plants at all stages of development, resulting in severe loss of productivity. In response to unfavorable temperatures, plant biomolecules such as stress proteins, enzymatic and non-enzymatic antioxidants, organic osmolytes and phytohormones come into play, usually, as a part of the plant defense mechanisms. The accumulation of these molecules, which may be useful as metabolic indicators of stress tolerance, depend on the plant species exposed to the temperature stress, its intensity and duration. Some of these molecules such as osmolytes, non-enzymatic antioxidants and phytohormones may be supplied exogenously to improve temperature stress tolerance. Legumes show varying degrees of sensitivity to high and low-temperature stresses, which reduces their potential performance at various developmental stages. To address the ever-fluctuating temperature extremes that various legumes are being constantly exposed, efforts are being made to develop tolerant plant varieties via conventional breeding methods as well as more recent molecular breeding techniques. In this review, we describe the progress made towards the adverse effects of abnormal temperatures on various growth stages in legumes and propose appropriate strategies to resolve these effects.