Phytohormone involved in salt tolerance regulation of <i>Elaeagnus angustifolia</i> L. seedlings

Soil salinization is a serious problem for plant growth worldwide. Understanding the tolerance mechanisms of salt-tolerant plants is essential for development and utilization of saline-alkali land. The salt-tolerant tree species <i>Elaeagnus angustifolia</i> is utilized in landscaping and ecological restoration projects such as afforestation. In this work, we examined the changes in phytohormone levels and the expression of phytohormone-related genes in <i>E. angustifolia</i> seedlings under salt stress. We observed no changes in the biomass, leaf area, and the size of epidermal cells of <i>E. angustifolia</i> seedlings under low levels of NaCl (50 mM); however, when the NaCl concentration was increased, these parameters were significantly reduced. Comparison of the transcriptome data of the species seedlings under 0 and 150 mM NaCl showed that many hormone pathways are involved in the salt-tolerance response. Under salt stress, abscisic acid (ABA) and jasmonate (JA) contents increased significantly, whereas the contents of auxin (IAA), gibberellin (GA), cytokinins (CKs), and brassinosteroids (BRs) decreased significantly. We conclude that these changes could be responsible for the growth inhibition and increased salt resistance of <i>E. angustifolia</i> seedlings.