Climate-driven soil acidification and salinity shape xylem architecture in the mangrove Aegiceras corniculatum

Mangrove xylem development is shaped by multiple interacting environmental drivers, yet it remains unclear whether vessel traits primarily follow a salinity-dominated pattern or a more integrated climatic-edaphic framework. Here, we combined field surveys, controlled pot experiments, and structural equation modeling (SEM), together with transcriptomic profiling, to disentangle the relative contributions of climate, soil properties, and developmental regulation to xylem architecture in Aegiceras corniculatum. We found that temperature and precipitation regimes significantly modified soil chemistry-particularly by driving acidification and salinization-which jointly accounted for most of the variation in wood anatomical traits. Contrary to the prevailing "salinity-centric" view, soil pH emerged as the dominant driver of vessel diameter and vessel area, whereas vessel density responded to the combined effects of salinity and nutrient dynamics. These shifts produced clear seasonal differentiation in growth rings and a coordinated adjustment of vessel diameter and density. Transcriptome analyses further revealed a set of candidate transcription factors (including WRKY, ABF, and NAC/MYB families) that integrate stress perception with secondary cell-wall biosynthesis, suggesting a mechanistic basis for anatomical plasticity. Together, our findings highlight a soil-mediated pathway through which climatic factors influence mangrove hydraulic strategies, offering new insights into the adaptive coordination between vessel architecture, transcriptional regulation, and the heterogeneous intertidal environment.