Anatomical and chemical traits associated with sheath-mediated protection in two Pantanal palms.

BACKGROUND AND AIMS: Attalea phalerata and Copernicia alba are dominant palms in the fire-prone wetlands of the Pantanal, where they frequently survive recurrent fires. Because their overlapping persistent leaf sheaths remain attached to the stipe and are the first structures exposed to heat and flames, they may contribute to thermal protection. This study investigated the anatomical and phytochemical traits of the leaf sheath to assess its potential contribution to fire resistance. METHODS: We compared leaf sheaths from burned and unburned individuals using anatomical analyses, histochemistry, and quantification of total phenolics and tannins by the Folin-Ciocalteu assay. KEY RESULTS: In both species, the leaf sheath showed extensive sclerenchyma, forming a dense protective matrix. In A. phalerata, this matrix included a thick surrounding sclerenchymatous zone containing meristematic cells, suggesting potential for new cell formation and tissue renewal after damage. In C. alba, unburned sheaths showed markedly higher concentrations of total phenolics and tannins, whereas lower concentrations were detected in individuals sampled after fire, consistent with a role for these compounds in the post-fire chemical response. CONCLUSIONS: The persistent leaf sheath is associated with traits that may contribute to stem and apical meristem protection in both species. Although both palms combine structural and chemical attributes, the results suggest different functional strategies, with A. phalerata showing stronger structural reinforcement and C. alba showing greater constitutive investment in phenolic compounds.