Ontogeny and structure of the pericarp and the seed coat of Miconia albicans (Sw.) Triana (Melastomataceae) from " cerrado" , Brazil

Abstract

-(Ontogeny and structure of the pericarp and the seed coat of Miconia albicans (Sw.) Triana (Melastomataceae) from "cerrado", Brazil). Miconia albicans fruit and seed coat ontogeny were described under light microscope. The samples were fixed in formalin-aceto-alcohol (FAA), neutral-buffered formaldehyde solution (NBF) and formalin-ferrous sulphate (FFS) solutions, embedded in plastic resin, sectioned at 10 µm and stained with Toluidine Blue. Specific dyes and/or reagents were used for the microchemical tests. The ovary is semi-inferior and the indehiscent, fleshy globose berries are originated mainly from the development of the inferior portion of the ovary. The immature pericarp is mainly parenchymatous with some sclereids, druse crystal and phenolic-like compounds idioblasts widespread in the mesocarp. In the mature pericarp, the endocarp cells are often collapsed, the mesocarp is thick with cells more or less turgid, and the sclereids, the druses and the phenolic-like compound idioblasts are almost absent. The ovules are anatropous, bitegmic and crassinucellate, and the zig-zag micropyle is formed by both the exostome and the endostome. The mature seed is pyramidal-elongated in shape, exalbuminous and testal. The raphal part occupies about 40% of the seed coat total length and had the mechanical layer derived from its inner layer. The antiraphal side is non-multiplicative and the exotesta, mesotesta and endotesta are differentiated into a sclerotic layer, with the exotesta being the mechanical one. The tegmen is absent.Key words -anatomy, fruits, Melastomataceae, Miconia, ontogeny RESUMO -(Ontogenia e estrutura do pericarpo e do envoltório da semente de Miconia albicans (Sw.) Triana (Melastomataceae) do cerrado, Brasil). A ontogenia dos frutos e das sementes de M. albicans foi descrita sob microscopia de luz. Os materiais foram fixados em soluções de formalina -ácido acético -álcool etílico 50% (FAA), formalina neutra tamponada (FNT) e sulfato ferroso em formalina (SFF), embebidos em resina plástica, seccionados a 10 µm de espessura e corados com Azul de Toluidina. Corantes e/ou reagentes específicos foram usados para os testes microquímicos. O ovário é semi-ínfero, e os frutos são bagas indeiscentes, originadas em sua maior parte a partir do desenvolvimento da porção ínfera do ovário. O pericarpo imaturo é principalmente parenquimático, com esclereídes, idioblastos cristalíferos e com compostos fenólicos no mesocarpo. No pericarpo maduro as células do endocarpo estão freqüentemente colapsadas, o mesocarpo é espesso, com células túrgidas, e as esclereídes e os idioblastos cristalíferos e com compostos fenólicos estão em pequena quantidade. Os óvulos são anátropos, bitegumentados e crassinucelados, e a micrópica, em zig-zag, é formada pelo exóstoma e pelo endóstoma. A semente madura é piramidal-alongada, exalbuminosa e testal. A porção rafeal ocupa aproximadamente 40% do comprimento total da semente e possui a camada mecânica derivada de suas camadas internas. A porção anti-rafeal é não-multiplicativ...

Interactions between Ants and Non‐myrmecochorous Fruits in Miconia (Melastomataceae) in a Neotropical Savanna

“…During the dry season, fire is a recurrent phenomenon across the cerrados of Brazil (Simon et al 2009). Miconia berries usually have high water and sugar content (Cortez & Carmello-Guerreiro 2008), and are an important resource consumed by many bird species (Renner 1989, Stiles & Rosselli 1993, Silveira et al 2012a. Miconia berries usually have high water and sugar content (Cortez & Carmello-Guerreiro 2008), and are an important resource consumed by many bird species (Renner 1989, Stiles & Rosselli 1993, Silveira et al 2012a.…”

“…STUDY SPECIES.-Melastomataceae is one of the most species-rich plant families in the cerrado; our studies were conducted with six species from the genus Miconia. Miconia berries usually have high water and sugar content (Cortez & Carmello-Guerreiro 2008), and are an important resource consumed by many bird species (Renner 1989, Stiles & Rosselli 1993, Silveira et al 2012a. A large fraction of fruits, however, are not removed by frugivores, but instead fall to the cerrado surface, where they are available to the ant community (Christianini & Oliveira 2009).…”

The ontogenetic bases for variation in ovary position in Melastomataceae

“…Among the species sampled, Microlicia euphorbioides , Rhynchanthera grandiflora , and Tibouchina clinopodifolia have dry, dehiscent fruits (“capsules”); Henriettea saldanhae , Leandra melastomoides , and Minonia dodecandra have fleshy and indehiscent fruits (“berries”) (Martins et al, 2009). The most consistent relation of the ovary position is with fruit dehiscence: indehiscent fruits are associated with the presence of gynoecial hypanthia (inferior ovaries), while dehiscent fruits are found in the absence of a gynoecial hypanthium (superior ovaries) (Clausing et al, 2000; Cortez and Carmello‐Guerreiro, 2008). However, the fruits of Melastomataceae have wide structural heterogeneity (see Baumgratz, 1985; Clausing et al, 2000), which makes the mentioned relation an oversimplification.…”

Two new species of <I>Leandra</I> s. str. (<I>Melastomataceae</I>) from the Atlantic Forest in Espírito Santo, Brazil

“…), but seldom in the same quantity. Perhaps these strongly abundant druses act on repelling herbivores (Cortez & Carmello-Guerreiro 2008), in the same way that trichomes do (Paleari & Santos 1998), and in a certain sense, may compensate for the absence of trichomes in an essentially glabrous plant. Reginato & R.Goldenb., sp.nov.…”