948 resultados para lotus embryo
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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In diplopods, the presence of calcium-containing structures seems to be a common finding in some species, with its formation being similar to that observed for other intracellular mineralization systems. In the present study, using histochemistry and transmission electron microscopy, a large amount of calcium was observed in the oocytes of Rhinocricus padbergi. Calcium was detected in both less and well developed oocytes, i.e., the occurrence of calcium coincided with the beginning of vitellogenesis. Calcium was observed as fine granulation distributed within the cytoplasm or deposited in spherical structures apparently formed by overlapping calcium layers. Some authors have suggested that these structures represent a type of reserve used for the calcification of the embryo exoskeleton, whereas others believe that calcium inclusions are a mechanism of organism detoxification as a result of excess calcium ingested by animals during soil turnover. We suggest in this paper that the first hypothesis could be occurring in R. padbergi since at the juvenile stages of the individuals the uptake of calcium is low and because the oocyte is a specialized cell not associated with detoxification.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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The developmental anatomy and morphology of the ovule and seed in several species of Heliconia were investigated as part of an embryological study of the Heliconiaceae and to provide a better understanding of their relationships with the other families of the Zingiberales. Heliconia species have an ovule primordium with an outer integument of both dermal and subdermal origin. The archesporial cell is divided into a megasporocyte and a single parietal cell, which in turn are divided only anticlinally to form a single parietal layer, disintegrating later during gametogenesis. The embryo sac was fully developed prior to anthesis. In the developing seed, the endosperm was nuclear, with wall formation in the globular stage; a nucellar pad was observed during embryo development, but later became compressed. The ripe fruit contained seeds enveloped by a lignified endocarp that formed the pyrenes, with each pyrene having an operculum at the basal end; the embryo was considered to be differentiated. Most of these characteristics are shared with other Zingiberales, although the derivation of the operculum from the funicle and the formation of the main mechanical layer by the endocarp are unique to the Heliconiaceae.
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The embryology and seed structure of Blastocaulon scirpeum (Mart.) Giul. and Paepalanthus scleranthus Ruhland were studied in order to contribute to the embryology of Eriocaulaceae and supply data for future taxonomic studies. Both species present: anther with 4-layered wall; conspicuous endothecium with fibrous thickenings; secretory tapetum with uninucleate cells; successive microsporogenesis forming isobilateral microspore tetrads; bicellular pollen grains; orthotropous, bitegmic and tenuinucellate ovule; micropyle formed by the inner integument alone; megagametophyte of the Polygonum type, with a conspicuous antipodal cyst; nuclear and starchy endosperm; reduced, undifferentiated, and bell-shaped embryo; operculate and endotestal seed; seed coat derived from the two ovule integuments; and tanniniferous endotegmen. In addition, Blastocaulon scirpeum shows a bisporangiate anther and a 3-layered ovary wall, while P. scleranthus presents a tetrasporangiate anther that becomes bisporangiate at maturity, and a 2-layered ovary wall. This investigation shows that the bisporangiate condition does not suffice to separate Blastocaulon from Paepalanthus, since it is common to both. It also indicates, based on several embryological aspects, the proximity of Eriocaulaceae and Xyridaceae, which comply mainly with the features presented by the other commelinid families. These results may be used in future cladistic analysis of the family, and contribute to a better understanding of its phylogeny.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Foram descritos e ilustrados aspectos morfo-anatômicos das sementes de Esenbeckia grandiflora Mart., visando o conhecimento dos tegumentos, endosperma e embrião. As sementes são de elipsóides a piramidais, marrom-escuras, anátropas, mesotestais, sem tégmem, exariladas e exalbuminosas. O embrião é axial, reto, total, branco, com cotilédones carnosos de reserva lipo-protéica, eixo hipocótilo-radícula curto e plúmula reduzida.
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Foram descritos e ilustrados aspectos morfo-anatômicos das sementes de Dictyoloma vandellianum Adr. Juss., visando o conhecimento dos tegumentos, endosperma e embrião. As sementes são reniformes, aladas, acobreadas, mesotestais, exariladas e albuminosas (reserva protéica). O embrião é axial, curvo, dominante, com cotilédones carnosos de reserva protéica, eixo hipocótilo-radícula longo e plúmula reduzida.
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Foram descritos e ilustrados aspectos morfoanatômicos das sementes de Balfourodendron riedelianum (Engler) Engler, visando a caracterização dos tegumentos, endosperma e embrião. As sementes são elipsóides, pretas, anátropas, endotestais com tégmem reduzido, exariladas e albuminosas. O endosperma possui reserva lipo-protéica. Embrião axial, dominante, branco, com cotilédones carnosos, eixo hipocótilo-radícula curto e plúmula reduzida.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)