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Amazon; leaf anatomy; leaf morphology; xeromorphism; cuticula; epidermis; sclerophylly
Abstract:
Leaf anatomy and morphology in eleven common arboreal species representing eleven families from Central Amazonian floodplain forests (Brazil) were analysed with SEM microscopy. Species differed in leaf-fall behaviour (evergreen, deciduous) as well as in the fate of submerged leaves (species either shed or keep their submerged leaves). Leaves of all species showed various traits generally related to leathery leaves and/or xeromorphism, e.g., large epidermal cells, thick outer epidermis walls, thick cuticula, compact spongy parenchyma with only few and small intercellular spaces, sunken stomata, and transcurrent vascular bundles with a strong sclerenchymatous bundle sheath. We found no trend to differentiate evergreen from deciduous species by leaf morphology and anatomy. Species that shed their submerged leaves showed similar characteristics than species that keep their submerged leaves. A high level of screlophylly in most species suggests that the trees might experience water stress in their floodplain habitats, independent of leaf-fall behaviour. However, as leathery and/or xeromorphic leaf are the typical pattern in tropical trees, leaf structures found here are unlikely to represent adaptations to floodplain conditions. Keeping submerged leaves apparently does not require different or additional morphological or anatomical characteristics
