Plant hormonesregulate plant growth and development by affecting an array of cellular,physiological, and developmental processes, including, but not limited to, celldivision and elongation, stomatal regulation, photosynthesis, transpiration,ion uptake and transport, initiation of leaf, flower and fruit development, andsenescence. Environmental factors such as salinity, drought, and extremetemperatures may cause a reduction in plant growth and productivity by alteringthe endogenous levels of plant hormones, sensitivity to plant hormones, and/or signallingpathways. Molecular and physiological studies have determined that planthormones and abiotic stresses have interactive effects on a number of basicbiochemical and physiological processes, leading to reduced plant growth anddevelopment. Various strategies have been considered or employed to maximizeplant growth and productivity under environmental stresses such as salt-stress.
A fundamental approach is to develop salt-tolerant plants through genetic means.Breeding for salt tolerance, however, is a long-term endeavour with its owncomplexities and inherent difficulties. Such extensive processes have delayeddevelopment of successful salt-tolerant cultivars in most crop species. Analternative and technically simpler approach is to induce salt tolerancethrough exogenous application of certain plant growth–regulating compounds.
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Planthormones (auxins, gibberellins, cytokinins, abscisic acid, ethylene, andbrassinosteroids) as well as several other plant growth–regulating substances(jasmonates, salicylates, polyamines, triacontanol, ascorbic acid, andtocopherols) have beneficial roles on plant stress tolerance. Brassinolide isan important steroidal component obtained from pollen grains of Brassicanapus L. and salicylic acid is a phenolic compound obtained from bark ofwillow tree (Salix sp.). Both BRs and SA are affecting plant growth anddevelopment in many different ways. These willassist in developing predictive models to modulate various useful traits inplants and address current challenges in agriculture.