Effect of salinity stress on hormones of auxin, gibberellin, physiological, morphological and anatomical characteristics of Hibiscus escolentus L.

Salinity stress is recognized as one of the most important factors limiting plant growth. Auxin and gibberellin are one of the most important plant hormones, with the smallest variation in their levels causing extensive responses throughout the plant. It has been shown that these two hormones are introduced to environmental stresses in tandem with other hormones in order to adapt the plant to new conditions. The aim of this study was to evaluate the changes in auxin and gibberellin hormones and its relationship with changes in the physiology, anatomy and morphology of okra plant under the influence of salt stress. In this study, okra plants were exposed to salinity treatments (0, 50, 100 and 150 mM NaCl) for 7 days. After treatment, root and stem length, fresh and dry weight, auxin and gibberellin levels were measured. The results showed that the levels of auxin and gibberellin hormone decreased significantly under salinity stress. In addition, the activity of the enzyme auxin oxidase increased. In this study, the Na+/K+ ratios and electrical conductivity increased while potassium and relative water content decreased. Structural studies showed that the thickness of different organs (root, stem and leaf) and the stomatal index decreased. The study showed that the length of the spongy and palisade mesophilic cells decreased under salinity stress, and the reduction in leaf thickness is more related to the reduction in palisade mesophilic. This research enhanced our understanding about the commercial use of hormones in oredr to reduce environmental stresses.