Adaptation of Carum carvi L. to high altitudes: investigating the effect of altitude on seed physiological dormancy

Background: The relationship between altitude and seed dormancy in high-mountain plants, particularly in Carum carvi L., reveals significant insights into how environmental conditions influence seed viability and germination. Objective: This research investigated the role of different C. carve habitats, with an emphasis on how altitude variations affect seed dormancy parameters. Methods: Three seed populations from altitudes of 650, 1200, and 2200 m a.s.l. were collected. Germination and viability tests, as well as analyses of biochemical parameters (primarily plant hormonal and antioxidant components), were carried out. Results:Seed germination rates were significantly lower at the highest altitude compared to lower elevations. This reduction was linked to enhanced seed dormancy, which correlated with elevated abscisic acid (ABA) concentrations, suggesting ABA's key role in altitude-dependent dormancy regulation. Concurrently, gibberellins (GAs) levels rose at higher altitudes, implying their contribution to improved germination traits and survival adaptation. Among endogenous compounds, xanthophylls (e.g., lutein, neoxanthin, violaxanthin, and antheraxanthin) exhibited a positive altitudinal trend, whereas α-tocopherol levels remained unchanged.Conclusion: These findings suggest that the lower temperatures and harsher conditions at higher altitudes significantly influence seed viability, germination, and dormancy. The physiological mechanisms, particularly the accumulation of ABA and the increase in xanthophylls, indicate an evolutionary adaptation that enhances survival under extreme environmental conditions. This adaptation is crucial for the persistence of high-mountain plant populations in Iran, where climatic challenges are pronounced.