Item

Abstract

Leaf anatomy and morphology in 23 common arboreal species representing 20 families from Central Amazonian white- (varzea) and blackwater (igapo) floodplain forests (Brazil) were analyzed with SEM microscopy. Species differed in leaf-fall behavior (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. No trend was found 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, significant differences were found only in the leathery appearance and the thickness of the outer wall and cuticula. Keeping submerged leaves apparently does not require major morphological or anatomical modifications. Species from the nutrient rich varzea showed similar characteristics as species of the nutrient poor igapo. When the present data set was combined with data from a previous study (total of 34 species) the frequency of two leaf characters was significantly different between floodplain types with igapo species showing a somewhat higher degree of xeromorphism. As leathery and/or xeromorphic leaves are the typical pattern in tropical trees, leaf structures found here are unlikely to represent adaptations to floodplain conditions. The scarcity of similarities in confamiliar or congeneric species also gives further evidence for this interpretation. The relation of xeromorphism with drought resistance and nutrient deficiency in Central Amazonian floodplains is discussed