Differential response of plasma membrane versus chloroplast functions to freeze-thaw stress by Antarctic species, Deschampsia antarctica and Colobanthus quitensis, as explored through freeze-injury and post-thaw recovery.

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conclusionAntarctic plants employ distinct cold acclimation strategies: Deschampsia antarctica uses general membrane-chloroplast stabilization while Colobanthus quitensis relies on chloroplast-focused tolerance mechanisms. The two native vascular plants of Antarctica, Deschampsia antarctica and Colobanthus quitensis, persist in one of the most extreme terrestrial environments on Earth, where episodic freeze-thaw cycles are frequent even during the growing season. Survival under such conditions necessitates not only tolerance to freezing alone but also effective recovery from freeze-induced injuries-a composite trait referred to as freeze-thaw stress tolerance (FTST). Yet, estimates of FTST of Antarctic plants have remained inconsistent across studies, largely due to methodological differences in freezing regimes and injury assessment metrics. Here, we employed a standardized, ice-nucleation-controlled freeze-thaw protocol and assessed FTST using two independent physiological indicators: electrolyte leakage (membrane integrity) and chlorophyll fluorescence (Fv/Fm; PSII function). We further validated the LT