The role of plant growth regulators in enhancing crop yield under saline conditions: from theory to practice

Intensified salinization of water and soil resources has promoted interest for research and approaches of improving crop yield under saline conditions. Reviewing the literature showed that the records on understanding of different aspects of salt stress and enhanced salinity tolerance in the world goes back to more than a century. Different approaches have been suggested to increase crop yield under saline conditions, among which one is using plant growth regulators (PGRs). Application of PGRs has begun since 1930s and their global annual sales are about US$ 1.2 billion. Nearly 40 active ingredients og PGRs are now in use, applied either as a single or combined treatments, among which the most important are auxins, cytokinins, gibberellins, ethylene, abscisic acid, brassinosteroids, salicylic acid, chlormequat chloride, paclobutrazol, jasmonic acid, ascorbic acid, triacontanol, strigolactones, nitric oxide, polyamines and plant peptide hormones. There have been large body of reports showing quantitative and quality improvement of crops as well as salinity tolerance as the consequences of PGRs application.However, most of these studies were conducted under controlled conditions (i.e. out of field conditions), as one season experiments, and this makes the results unreliable. In this paper, with having in mind the applicability for the field conditions, crop yield improvement as the result of using PGRs has been reviewed.