Response differences in seed germination and seedling growth of three Asteraceae plants under saline-alkali stress

Soil salinization severely restricts plant growth and threatens ecological sustainability, particularly in soda saline-alkali regions such as the Songnen Plain. Asteraceae plants are widely used in vegetation restoration due to their strong ecological adaptability. In this study, Tagetes erecta L., Cadendula officinalis L., and Leucanthemum maximum (Ramood) DC were selected as experimental materials. Two types of stress (salt and alkali) were applied at five concentration levels each (excluding the distilled-water control), which respectively constituted a salinity gradient and an alkalinity gradient. Seed germination parameters, seedling growth traits, and physiological indicators were measured, and field validation was conducted in areas with mild, moderate, and severe saline-alkali soils in the Songnen Plain. T. erecta L. showed optimal germination at the low concentration of salt and alkalinity (25 mmol/L), exhibiting a "low promotion and high inhibition" pattern, and maintained relatively high vigor under high stress. L. maximum had the highest germination rate under non stress conditions but was highly sensitive to increasing salt and alkalinity, while its root growth remained relatively stable under salt stress. C. officinalis L. was highly sensitive to alkali stress. Alkali stress consistently exerted stronger inhibitory effects on seed germination and seedling growth than salt stress. Field validation further demonstrated that T. erecta L. maintained a significantly higher survival rate under severe saline-alkali conditions (HS) compared to L. maximum and C. officinalis L. (p < 0.05). This study identified interspecific differences in saline-alkali tolerance among three Asteraceae species, offering a data basis and scientific reference for plant selection and breeding in ecological restoration and landscaping of saline-alkali areas.