Hormonal priming with indole-3-acetic acid modulates antioxidant defense, gene expression, and physiological...

Soil salinization is a major environmental challenge, limiting agricultural productivity and threatening ecological sustainability worldwide. Limonium spp., a halophytic genus with moderate salt tolerance, holds promise for revegetation and restoration of saline-affected lands. However, under severe salinity, its growth and physiological performance are adversely affected, highlighting the need for strategies to enhance its resilience. In this study, the potential of IAA priming to mitigate salinity-induced damage was evaluated in two Limonium cultivars, sky light and deep blue.

One-month-old plants were exposed to 250 mM NaCl, with or without prior priming with IAA. To evaluate the effect of IAA on salt stress mitigation, morphological, physiological, biochemical and molecular investigations were carried out.

Salt stress markedly impaired plant growth, reduced relative water content, chlorophyll content, and photosynthetic efficiency, while increasing Na⁺ accumulation, electrolyte leakage, lipid peroxidation, and oxidative stress. By contrast, IAA priming (20mM) alleviated these detrimental effects by enhancing osmotic adjustment, maintaining K⁺/Na⁺ homeostasis, improving chlorophyll retention, and reinforcing the antioxidant defense system. Proline accumulation, total soluble protein content, and stomatal regulation were also positively influenced by IAA treatment. Also, the expression of salt-responsive genes (RD22, RD29A, SOS1, AtP5CS1, LbMYB48, and LbAPX3) was upregulated under salinity, with a stronger induction observed in IAA-primed plants.

These findings highlight the regulatory role of IAA in modulating physiological, biochemical, and molecular responses to salinity stress, thereby enhancing the salt tolerance of limonium. The study underscores the potential of IAA priming as a practical strategy for improving the performance of plants under salinity to support the restoration of saline ecosystems.