Improving Performance of Salt-Grown Crops by Exogenous Application of Plant Growth Regulators

Abstract

Soil salinity is one of the major abiotic stresses restricting plant growth and development. Application of plant growth regulators (PGRs) is a possible practical means for minimizing salinity-induced yield losses, and can be used in addition to or as an alternative to crop breeding for enhancing salinity tolerance. The PGRs auxin, cytokinin, nitric oxide, brassinosteroid, gibberellin, salicylic acid, abscisic acid, jasmonate, and ethylene have been advocated for practical use to improve crop performance and yield under saline conditions. This review summarizes the current knowledge of the effectiveness of various PGRs in ameliorating the detrimental effects of salinity on plant growth and development, and elucidates the physiological and genetic mechanisms underlying this process by linking PGRs with their downstream targets and signal transduction pathways. It is shown that, while each of these PGRs possesses an ability to alter plant ionic and redox homeostasis, the complexity of interactions between various PGRs and their involvement in numerous signaling pathways makes it difficult to establish an unequivocal causal link between PGRs and their downstream effectors mediating plants’ adaptation to salinity. The beneficial effects of PGRs are also strongly dependent on genotype, the timing of application, and the concentration used. The action spectrum of PGRs is also strongly dependent on salinity levels. Taken together, this results in a rather narrow “window” in which the beneficial effects of PGR are observed, hence limiting their practical application (especially under field conditions). It is concluded that, in the light of the above complexity, and also in the context of the cost–benefit analysis, crop breeding for salinity tolerance remains a more reliable avenue for minimizing the impact of salinity on plant growth and yield. Further progress in the field requires more studies on the underlying cell-based mechanisms of interaction between PGRs and membrane transporters mediating plant ion homeostasis.

Regulation of Reactive Oxygen Species and Antioxidant Defense in Plants under Salinity

“…The Ca 2+ signaling persuaded by ROS signaling participates in AsA biosynthesis [3]. Several research reports demonstrated that exogenous application of hormones and signaling molecules regulated or enhanced the antioxidant defense system, conferred osmoprotection and improved physiology, which defended against oxidative damage under salt stress conditions [147][148][149]. There might be other hormones/hormonelike molecules or signaling molecules in this complex and hazy salt stress adaptation pathway.…”

Foliar Application of Salicylic Acid Improves Salt Tolerance of Sorghum (Sorghum bicolor (L.) Moench)

“…It seems that using other methods that are cost-time-effective are more suitable to reduce the harmful effects of salinity and should be taken into consideration [19]. Various studies have shown that exogenous application of growth regulators can reduce the harmful effects of salinity on plants, and it seems to be a practical way to cope with salt stress [20][21][22]. Salicylic acid (SA) is a plant phenolic compound that stimulates various biological processes in plants as a growth regulator [23,24].…”

Role of Promising Secondary Metabolites to Confer Resistance Against Environmental Stresses in Crop Plants: Current Scenario and Future Perspectives

“…IAA is involved in plant growth and development, as well as controlling growth in response to stress ( Casanova-Sáez et al, 2021 ; Kou et al, 2022 ; Mishra et al, 2022 ). IAA is important for plant tolerance to salt ( Quamruzzaman et al, 2021 ) and heavy metal stress ( Mathur et al, 2022 ). Auxins also cause the transcription of the major auxin response genes, which have been discovered in rice, Arabidopsis, and soybean ( Ahmad et al, 2010 ).…”