The phenotypic and physiological response mechanisms of Tetracentron sinense, an endangered plant and a relict from the tertiary period, to global warming.

Tetracentron sinense, an endangered relict species surviving since the Quaternary Period, was investigated to assess its adaptive responses to climate warming. A downward transplantation experiment simulated warming effects by transferring plants from a high-altitude site (2448 m) to a low-altitude site (2023 m). We analyzed seed germination traits, seedling survival dynamics, and adaptive mechanisms through phenotypic plasticity and physiological adjustments. Downward transplantation significantly enhanced germination percentage, vigor, and index, while reducing seedling survival-evidenced by cumulative survival decline and elevated mortality. Mortality peaked during the first month post-transplantation, creating a critical survival bottleneck. Physiological analyses revealed stable chlorophyll a, b, and a/b ratios, alongside stable total chlorophyll content and improved photosynthetic capacity. Plants alleviated low-altitude stress by accumulating osmoregulatory compounds: soluble sugars, proteins, and proline. Furthermore, catalase activity significantly increased, whereas peroxidase activity correspondingly decreased under this stress regime. In summary, while climate warming may compromise T. sinense early seedling survival, surviving individuals exhibit adaptive potential through enhanced phenotypic plasticity and physiological adjustments under warming-induced selective pressure.