Comparative leaf morphology and anatomy of three Asteraceae species

By Patrícia Milan, A. H. Hayashi, B. Appezzato‐da‐Glória. 2006

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ABSTRACT The objective of this paper was to describe and compare the morphology and anatomy of mature leaves of Mikania glomerata Spreng., Porophyllum ruderale Cass. and Vernonia condensata Baker (Asteraceae) species that have different habits emphasizing their secretory structures. Longitudinal and transversal sections of mature leaf blades of the three species were analyzed at the apex, base, and medium third part of the midvein of the leaf blade and of the margin. M. glomerata had uniseriate glandular trichomes and secretory ducts; P. ruderale had hydathodes and secretory cavities; and V. condensata had idioblasts and uni- and biseriate glandular trichomes. Key words: Mikania glomerata, Porophyllum ruderale, Vernonia condensata, secretory structures, medicinal plants * Author for correspondence INTRODUCTION The Asteraceae family consists of approximately 25000 species (Barroso, 1986) included in over 1100 genera. These species frequently present herbaceous habits, although arboreous and voluble herbaceous habits also occur (Cronquist, 1981). Because of this variety of habits, the family presents various anatomical structures and in some cases ecological specialization may occur (Metcalfe and Chalk, 1950). Secretory structures are of great taxonomical interest and their restricted distribution has an important diagnosis value (Metcalfe and Chalk, 1950; Fahn, 1979). Frequently, in Asteraceae, they occupy distinct positions in different organs of the plant occurring in all, some or in only one organ (Solereder, 1908). Castro et al. (1997) reviewed the types of secretory structures in the leaves of seventy two representatives of the Asteraceae family from the cerrado vegetation in the Reserva Biologica de Mogi Guacu, Sao Paulo, Brazil. When analyzed together these secretory structures presented diagnosis value at genus level. Eight types of leaf secretory structures were mentioned: ducts, cavities, idioblasts, laticifers, hydathodes, extrafloral nectaries, trichomes and glandular appendixes. According to Metcalfe and Chalk (1950), anatomical diversity is commonly observed in the structure of leaves of species belonging to the Asteraceae. Among the features that vary are: (a) stomata distribution on leaf surfaces; (b) guard-cell positioning in relation to ordinary epidermal cells; (c) hypoderm development on the upper side of the leaf surface; (d) mesophyll and fibrovascular system differentiation; and (e) wax secretion on leaf surface (Solereder, 1908). The anatomical features that can be observed in Asteraceae are: (a) presence of various types of glandular or covering trichomes; (b) papillae on

Subfields: Cancer Research, Ecology, Evolution, Behavior and Systematics, Plant Science

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