Comparative seed-level lithium tolerance in two ecotypes of Iranian Scrophularia striata Boiss.

Abstract Lithium (Li), as an emerging environmental contaminant, can disrupt plant physiological processes, underscoring the importance of investigating tolerant species to identify suitable candidates for restoring contaminated soils. This study assessed the impact of Li₂CO₃ and Li₂SO₄ (0, 50, 150, 250 mM) on seed germination and early growth of two drought-tolerant Scrophularia striata ecotypes, Lizan and Pahleh. Measured parameters included germination rate, final germination percentage (FGP), mean germination rate (MGR), germination index (GI), coefficient of velocity of germination (CVG), germination rate index (GRI), first and last germination time (FDG, LDG), time spread of germination (TSG), Timson index (TGI), seedling vitality index (SVI), seedling, root, and stem length, as well as fresh and dry weight. The Pahleh ecotype showed strong resistance to both Li forms at 50 and 150 mM, with a significantly higher MGR than the control at these concentrations. The Lizan ecotype maintained higher growth under Li stress, while Pahleh seedlings were about two times shorter under Li₂SO₄ and 1.5 times shorter under Li₂CO₃, indicating the superior Li tolerance of Lizan. The Pahleh ecotype showed no significant biomass change between the control and some Li concentrations. At 150 mM Li₂CO₃, the Pahleh ecotype showed no significant change in germination, indicating high Li tolerance. Li form and concentration influenced tolerance and growth in both ecotypes. S. striata, especially Lizan, appears suitable for Li-contaminated arid lands.