Role of Amino Acids other than Proline in Abiotic Stress Amelioration in Plants

Plants face number of stresses from their surroundings, of which, abiotic stresses, such as high salinity, drought, extreme temperatures and heavy metal toxicity, have a substantial impact on them. These stresses affect physiology, metabolism, development and produce of a plant, either by disturbing the normal functioning of various important activities of a plant or by generating reactive oxygen species (ROS). In response to these, plants accrue certain compatible solutes named as osmolytes, such as sugars, polyamines and amino acids etc., which constitute one of the significant stress tolerance mechanisms. Plants produce various types of amino acids viz. proline, glycine-betaine, aspartic acid, glutamate, lysine and methionine etc. to counteract the damaging effects of various stresses. Out of theses the role of proline in stress management is well documented. So the present review is mainly concerned about the role of amino acids other than proline in stress management in plants. This review describes the origin of different abiotic stresses, their phytotoxic effects, role of amino acids other than proline in amelioration of different abiotic stresses. Besides, the possible modes by which amino acids help to mitigate the damaging effects of various abiotic stresses such as by acting as biostimulants, as compatible solutes and as activator of antioxidative defence system are also discussed. Some key areas related to the potential exogenous application of amino acids to stressed plants and their molecular mechanisms need to be addressed so as to channelize the research in ensuring the sustainable use of amino acids.