Plant Performance and Defensive Role of Proline Under Environmental Stress

Plants are exposed to various kinds of abiotic and biotic stresses throughout their development which include salinity, drought, extremes temperature, heavy metal, and infection by pathogens, nutrient deficiency, and UV radiation. Amino acids have traditionally been considered as precursors to and constituents of proteins and play an important role in plant metabolism and development. Proline, an amino acid, plays an important role in plants. It protects the plants from various stresses and also helps plants to recover from stress more rapidly. If plants are exposed to stress, then proline applied exogenously results in increased growth and other physiological characteristics of plants. Also, they contain different types of functions like it is an osmolyte, ROS scavenger, redox balancer, cytosolic pH buffer, molecular chaperon, and a stabilizer of protein structure. Several reports have been developed about a correlation between the content of proline and plant resistance to unfavorable environmental factors. Proline accumulation occurs due to the stimulation of its synthesis from glutamic acid, the suppression of proline oxidation, or changes in its incorporation in protein synthesis. Under various stresses, proline is synthesized in the cytosol and chloroplasts. This chapter provides comprehensive view regarding the beneficial role of proline in plants under adverse environmental conditions.