Impact of the <i>etr1-1</i> Mutation, Impairing Ethylene Sensitivity, on Hormonal Status and Growth of <i>Arabidopsis thaliana</i> Under Salinity Stress

The role of ethylene in the adaptation of <i>Arabidopsis thaliana</i> to salt stress induced by 150 mM NaCl is investigated. The responses of wild-type (Columbia, WT) plants and ethylene-insensitive <i>etr1-1</i> mutants to short-term daily salt treatments were compared. Parameters analyzed included growth, water status, chlorophyll content, and hormone levels (ABA, IAA, cytokinins) using ELISA and immunohistochemistry. The results revealed that in the WT, salt stress induced hormonal redistribution: accumulation of ABA, IAA, and zeatin in shoots, accompanied by decreased ABA in the root tips and cytokinins in the whole roots. These hormonal changes were associated with stomatal closure, maintained leaf hydration, and inhibition of root growth. The inhibition of root growth may contribute to reduced uptake of toxic ions from the environment. In contrast, <i>etr1-1</i> mutants exhibited no changes in hormonal status, failed to close stomata—leading to decreased leaf water content—and showed a sharp decline in chlorophyll content accompanied by suppressed shoot growth. The conclusions emphasize that ethylene sensitivity is essential for initiating adaptive hormonal rearrangements that coordinate growth and stomatal responses to mitigate the effects of salt stress.