Abstract
<title>Abstract</title> <p> Halophytes are increasingly recognized for their salt-tolerance and their potential in soil restoration and saline agriculture. However, studies optimizing <italic>in vitro</italic> propagation and evaluating <italic>ex vitro</italic> performance to improve post-transplant growth and propagation efficiency remain scarce. This study demonstrates the effectiveness of <italic>in vitro</italic> techniques for selecting and propagating elite clones of <italic>Salicornia lagascae</italic> with enhanced salinity tolerance. Plants micropropagated in solid and liquid culture systems (S and L plants, respectively) were acclimated <italic>ex vitro</italic> and subsequently exposed to 30 (S30 and L30) or 60 (S60 and L60) g L⁻¹ NaCl for six weeks. Electrical conductivity was higher in shoots than in roots and substrate, indicating strong ion accumulation in aerial tissues, correlating with Na⁺ and Cl⁻ levels. L plants generally exhibited greater photosynthetic efficiency and enhanced non-photochemical energy dissipation under stress over time, while lower salinity promoted higher electron transport rates. High salinity decreased APX activity, while CAT, SOD, and POX activities were maintained, indicating effective oxidative stress control under severe salinity. Metabolomic analysis revealed strong separation of S30 plants, showing the greatest metabolic reprogramming, including activation of amino acid, carbohydrate, flavonoid, terpenoid, and stress-related secondary metabolic pathways. In contrast, plants exposed to 60 g L⁻¹ NaCl likely redirected energy toward survival and ion homeostasis, with more limited metabolic adjustments. Likewise, L plants exhibited more homogeneous metabolomic profiles, likely because liquid micropropagation enhanced physiological acclimation and reduced the need for large-scale metabolic reprogramming after transplantation. Overall, the remarkable salt tolerance of <italic>S. lagascae</italic> is supported by the coordinated action of ion homeostasis, photoprotective mechanisms, antioxidant defenses, and metabolic reprogramming. Results demonstrate that <italic>in vitro</italic> selection and micropropagation constitute efficient strategies for generating elite halophytic germplasm suitable for saline agriculture, phytoremediation, and soil restoration programs. </p>