Physiological priority over morphological growth: a resource trade-off strategy of the moss Hydrogonium majusculum (C. Muell.) Chen in petrifying spring tufa

BACKGROUND: The unique petrifying spring habitats formed by karst topography in Southern China harbor bryophyte communities dominated by the endemic species Hydrogonium majusculum (C. Muell.), which plays a crucial role in habitat maintenance and tufa deposition. However, the underlying adaptive strategies-specifically how H. majusculum coordinates morphological and physiological responses to adapt to such highly heterogeneous sedimentary dynamics-remain unclear. RESULTS: ), which serve as proxies for reduced calcification pressure, were significantly positively correlated with physiological traits (e.g., chlorophyll (Chl), superoxide dismutase (SOD), carbonic anhydrase (CA)) (p < 0.05), indicating that the physiological system is highly sensitive to the amelioration of low-energy sedimentary environments. (2) Conversely, morphological variation (e.g., plant height (Plant H) was predominantly restricted by physical calcification intensity (CaO). Although morphological traits exhibited localized growth in detritus-enriched sites, their overall structural recovery showed a distinct lag compared to physiological traits. This indicates that the rigid calcified crust continues to impose biomechanical constraints even as environmental stress decreases. CONCLUSIONS: Our data reveal a specific resource trade-off strategy of H. majusculum in dynamic petrifying spring habitats, which is characterized by physiological priority over morphological growth. Under high physical pressure, the moss sends energy to its enzymatic defense system first. This investment maintains cellular stability. The plant moves resources to carbon assimilation and growth only when local physical stress drops. This study explains how H. majusculum adapts to deposition dynamics. These findings also provide a theoretical basis for the management and protection of petrifying spring habitats.