Using Saline Water for Sustainable Floriculture: Identifying Physiological Thresholds and Floral Performance in Eight Asteraceae Species

Water scarcity challenges floriculture, which depends on quality irrigation for ornamental value. This study assessed short-term salinity tolerance in eight Asteraceae species by measuring physiological (proline levels, antioxidant enzyme activity) and morphological (plant height, flower number, and size) responses. Plants were irrigated with 0, 50, 100, or 300 mM NaCl for 10 days. Salinity significantly enhanced proline content and the activity of key antioxidant enzymes (catalase, peroxidase, and ascorbate peroxidase), reflecting the activation of stress defense mechanisms. However, these defenses failed to fully protect reproductive organs. Flower number and size were consistently more sensitive to salinity than vegetative traits, with significant reductions observed even at 50 mM NaCl. Responses varied between species, with Zinnia elegans and Calendula officinalis exhibiting pronounced sensitivity to salinity, whereas Tagetes patula showed relative tolerance, particularly under moderate stress conditions. The results show that flower structures are more vulnerable to ionic and osmotic disturbances than vegetative tissues, likely due to their higher metabolic demands and developmental sensitivity. Their heightened vulnerability underscores the need to prioritize reproductive performance when evaluating stress tolerance. Incorporating these traits into breeding programs is essential for developing salt-tolerant floriculture species that maintain aesthetic quality under limited water availability.