Mangrove ecosystems, vital for carbon sequestration and their unique adaptations to inundated environments, face increasing challenges from rising sea levels and elevated atmospheric CO 2 concentrations due to global climate change. Research is urgently needed to uncover the molecular mechanisms behind mangroves’ responses to these stressors, informing effective conservation and management strategies. In this study, we conducted phenotypic observations and transcriptome analyses on two pioneer mangrove species, Sonneratia apetala and Avicennia marina, under elevated CO 2 (eCO 2) and prolonged inundation conditions that simulate future climate scenarios of CO 2 rise and sea level increase. The two species exhibited distinct morphological and physiological responses: S. apetala showed minimal changes, while A. marina demonstrated accelerated growth and early flowering. Transcriptome analysis revealed molecular-level responses to these stressors, highlighting significant impacts on cell wall biosynthesis, plant hormones, and photosynthesis pathways. This study emphasizes the adaptability of mangroves to climate change and provides insights into their complex responses to eCO 2 and prolonged flooding. Ultimately, it offers valuable directions for future research on mangrove resilience and climate change adaptation.

As part of the plant water-use process, plant nocturnal sap flow ( Q n) has been demonstrated to have important ecophysiological significance to compensate for water loss. The purpose of this study was to explore nocturnal water-use strategies to fill the knowledge gap in mangroves, by measuring three species co-occurring in a subtropical estuary. The Q n existed persistently and contributed markedly over 5.5%~24.0% of the daily sap flow ( Q) across species, which was associated with two processes, nocturnal transpiration ( E n) and nocturnal stem water refilling ( R n). The diversity of stem recharge patterns and response to sap flow to high salinity conditions were the main reasons for the differences in Q n/ Q among species. For Kandelia obovata and Aegiceras corniculatum, R n was the main contributor to Q n, which driven by the demands of stem water refilling after diurnal water depletion and high salinity. In contrast, Avicennia marina maintained a low Q n, driven by vapor pressure deficit, and the Q n mainly used for E n, which adapts to high salinity conditions by limiting water dissipation at night. We conclude that the diverse ways Q n properties act as water-compensating strategies among the co-occurring mangrove species might help the trees to overcoming water scarcity.