Leaf anatomy and its contribution to the systematics of Aechmea subgenus Macrochordion (de Vriese) Baker (Bromeliaceae)

Ana Paula G De Faria,Tânia Wendt,Ana Claudia M Vieira

doi:10.1590/s0001-37652012005000053

Abstract

The leaf anatomy of the species Aechmea subgenus Macrochordion was analyzed to obtain valuable data on their taxonomic delimitation and to identify anatomical adaptations to their respective habitats and habits. All leaves of these species are hypostomatic, and present: peltate trichomes on both surfaces; stomata sunk in epidermal depressions; small epidermal cells with thick walls and inclusions of silica bodies; a mechanical hypodermis; an aquiferous parenchyma; chlorenchyma with fibrous clusters and air channels; and vascular bundles surrounded by a parenchymatic sheath and a cap of fibers. The results are evaluated within an adaptive and taxonomic context. Variations in hypodermic thickening, amount of water parenchyma, position of the air channels and shape of the cells filling the air channels are useful for delimiting groups of species, strengthening the relationships suggested by their external morphology.

Highlights

The Bromeliaceae includes 3,172 species (Luther 2008) and is a representative monocot family for Neotropical flora
The present study describes the foliar structure of Aechmea subgenus Macrochordion with the aim of providing additional morphological characters to support the systematic boundaries of the species, as well as identifying anatomical adaptations to their respective habitats
The leaf epidermis of Aechmea subgenus Macrochordion species is organized in a single layer of cells and in transverse section can be almost plane on both surfaces, as in A. lamarchei (Fig. 1A), undulating on the abaxial surface in A. bromeliifolia var. albobracteata (Fig. 1B) and A. triangularis (Fig. 1C) or on both surfaces, as in A. bromeliifolia var. bromeliifolia (Fig. 1D), A. alba (Fig. 1E) and A. maasii (Fig. 1F)

Summary

Introduction

The Bromeliaceae includes 3,172 species (Luther 2008) and is a representative monocot family for Neotropical flora. It occupies a basal position within the Poales order and is closely related to Typhaceae and Rapateaceae (APG III 2009). Some morphological and physiological adaptations to drier habitats and particular life forms out of the soil include the presence of a central tank (which allows the plant to collect water and organic material inside enlarged and overlapping leaf sheaths), leaves with absorbing scales (the most distinguishing feature of the family, referred to as peltate trichomes), water storage and mechanical support tissues, the development of ‘crassulacean acid metabolism’ (CAM) photosynthesis, and the progressive structural and functional reduction of root systems in epiphytic and rupiculous species (Tomlinson 1969, Benzing 1976, 2000a, b).

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Conclusion