Abstract

Plants are extremely subjected to environmental stress, which includes drought, low or high temperatures, and salt stress. The most common environmental stress factor is salinity, primarily in arid and semi-arid regions. Salinity stress is the most limiting factor for seed germination and plant productivity; therefore, most plants are susceptible to adverse effects because of the high concentration of salt in the soil, which affects plant growth and productivity. Phytohormone, considered an endogenous defense factor under stress conditions, has an important role in plant growth and survival, particularly under abiotic stress. Phytohormones influence a wide spectrum of processes in plants in both normal and stressful environments. The phytohormones stimulate plant responses to stress conditions, such as jasmonic acid, while there are other phytohormones that include Proline, Gibberellic acid, Cytokinins and Auxins. Exogenous application of plant growth regulators could be an alternate strategy to improve salt stress tolerance. The use of auxin or gibberellin has been shown to mitigate the violent effects of abiotic stresses on seed germination, plant growth, and productivity. Furthermore, proline induces plant tolerance against various abiotic stresses by increasing their endogenous levels and their intermediate enzymes in plants. Moreover, exogenous application of proline may be a good approach to reducing the unfavorable effects of salinity stress on plants.