Comparative proteomics of bark and xylem provides insights into age-dependent corticular photosynthesis in

Introduction: Eucalyptus species are globally important for forestry due to rapid growth, adaptability, high biomass production, and contribution to carbon sequestration by storing atmospheric CO Methods: We analyzed bark and xylem from 4- and 12-year-old clonal Results: Chloroplasts were more abundant in younger bark and were not detected in xylem. A total of 3,113 non-redundant proteins were identified, and enrichment analysis indicated a consistent hypoxic response across tissues and ages, alongside age-specific metabolic processes. Proteoform abundance patterns implicated glycolysis, the tricarboxylic acid cycle, and fermentation pathways. Alcohol dehydrogenase and aldehyde dehydrogenase proteoforms showed differential abundance in xylem and younger bark, consistent with greater emphasis on fermentative metabolism in hypoxia-prone vascular tissues. Younger bark also exhibited higher abundance of Calvin-Benson cycle proteins, together with higher chloroplast numbers than older bark and xylem, indicating higher potential for local carbon fixation and oxygen availability in juvenile stems. Discussion: These findings underscore adaptive metabolic strategies of eucalyptus stems, refine current models of corticular photosynthesis and stem energy metabolism in fast-growing trees, and provide a molecular framework for future physiological studies in eucalyptus and other woody species.