Calcium dominance, ion regulation, and metabolic defenses underlie salt tolerance in the halophyte <i>Azima sarmentosa</i>

Background: , a woody halophyte native to Southeast Asia, thrives in saline, calcium-poor soils, but its underlying tolerance mechanisms remain insufficiently described. This study investigated anatomical, physiological, and biochemical traits associated with salinity tolerance across a natural salinity gradient. Methods: Soils, stems, mature leaves, and young leaves were analyzed using ion quantification, scanning electron microscopy Energy Dispersive X-ray Spectrometer (SEM-EDS/EDX), synchrotron radiation X-ray tomographic microscopy (SRXTM), Fourier transform infrared spectroscopy (FT-IR) spectroscopy, and multivariate analyses (correlation and Principal Component Analysis (PCA)) to characterize Ca-, Na-, and metabolic-related responses. Results: grouped with EtOH-derived phenolics, highlighting a divergence between Ca-driven protection and Na-linked stress. Conclusion: -derived oxalate, linking ionic regulation with carbon cycling and broadening the ecological significance of calcium-mediated salt tolerance.