The resilience of the aquatic Isoetes cangae to terrestrial environment: Insights into molecular and ecophysiological adaptations

The Isoetes genus comprises a basal lineage of vascular plants with a wide distribution, including aquatic and terrestrial species, which can be attributed to environmental changes throughout its evolutionary history. The underwater quillwort, Isoetes cangae, is endemic to Lake Amendoim in the northern Amazon rainforest region of Brazil. To aid conservation strategies, we investigated the molecular and physiological changes associated with water column reduction and tolerance to terrestrial environments. Remarkably, this aquatic species has demonstrated a tolerance for periods without a water column during ex situ cultivation. Short-term experimental conditions (24 h) revealed upregulation of stress-related genes, while biochemical, morphological, and physiological parameters remained unchanged. In contrast, long-term terrestrial conditions (3-6 months) induced changes in the physiology and morphology of I. cangae, including an increase in antioxidant capacity, photoprotective mechanisms, and the preservation of reproductive structures. The Crassulacean Acid Metabolism was present in both aquatic and terrestrial conditions. Mature and immature spores were able to produce plants even after 12 months of desiccation, with desiccated spores generating more progeny than submerged spores.