Post-Salinity Stress Recovery of Black Calla Lily (Arum palaestinum Boiss.) Mediated by Plant Growth Regulators

Salinity stress severely limits growth, physiological function, and metabolic balance in the black calla lily (Arum palaestinum Boiss.), a medicinal and ornamental species native to Mediterranean regions. This study evaluated the effectiveness of selected plant growth regulators (PGRs) in enhancing black calla lily recovery following salinity stress. Seedlings were exposed to severe salinity (25 dS m−1) and subsequently treated with abscisic acid (ABA; 1.0–2.0 mM), salicylic acid (SA; 1.0–2.0 mM), fusicoccin (FC; 0.01–0.03 mM), or ethephon (E; 5–20 mM). Recovery was assessed using morphological, physiological, and biochemical indicators, including leaf color, leaf area, chlorophyll content, plant quality, K+/Na+ ratio, total nonstructural carbohydrates, reducing sugars, and proline content. All PGRs significantly improved recovery relative to untreated salt-stressed plants, with clear differences in efficacy. ABA was the most effective regulator, followed by ethephon, while SA and FC showed moderate benefits. Optimal ABA treatment (2.0 mM) resulted in near-complete recovery, characterized by improved leaf greenness and expansion, enhanced ionic homeostasis, increased carbohydrate reserves, and reduced accumulation of stress-related metabolites, particularly proline and reducing sugars, indicating alleviation of salinity stress and restoration of normal metabolic activity. These findings demonstrate that post-salinity recovery in A. palaestinum is strongly hormone-dependent and highlight the potential of ABA- and ethylene-based strategies to enhance salinity resilience.