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| Registros recuperados: 16 | |
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| Schols, P.; Furness, C.; Merckx, V.; Wilkin, P.; Smets, E.. |
| Pollen and orbicule ontogeny in representatives of three genera of Dioscoreales—Narthecium ossifragum Huds. (Nartheciaceae), Tacca artocarpifolia Seem. and Tacca chantrieri Andre´ (Dioscoreaceae), and Dioscorea communis (L.) Caddick & Wilkin (Dioscoreaceae)—is described and illustrated using LM, SEM, and TEM. The main difference is in microsporogenesis, which is successive in Narthecium Huds. and simultaneous in Tacca J.R. & G. Forst. and Dioscorea L. This is reflected in the tetrad configuration but not in the apertures: Narthecium and Tacca are monosulcate, while Dioscorea has two equatorial apertures. Other features of pollen development are similar in all three genera. Exine development starts at the proximal pole, and during the tetrad stage,... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Intine; Microsporogenesis; Monocotyledons; Orbicules; Pollen ontogeny; Systematics; Tapetum; Tetrads. |
| Ano: 2005 |
URL: http://www.repository.naturalis.nl/record/407299 |
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| Mendes-Bonato,Andréa Beatriz; Risso-Pascotto,Claudicéia; Pagliarini,Maria Suely; Valle,Cacilda Borges do. |
| Microsporogenesis was analyzed in an interspecific hybrid between an artificially tetraploidized sexual accession of Brachiaria ruziziensis (R genome) and a natural apomictic tetraploid accession of B. brizantha (B genome). Chromosomes associated predominantly as bivalents. From this phase to the end of meiosis, chromosomes presented irregular segregation and abnormal arrangement in the metaphase plate. During metaphase I, in 27.8% of meiocytes, bivalents were distributed in two metaphase plates. In anaphase I, two distinct and typical bipolar spindles were formed. In 29.7% of pollen mother cells, one genome did not divide synchronically, with chromosomes lagging behind or not segregating at all. The second division was very irregular, resulting in... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Brachiaria; Forage grass; Interspecific hybridization; Meiotic rhythm; Microsporogenesis. |
| Ano: 2006 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572006000400021 |
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| PAGLIARINI, M. S.; TAKAYAMA, S. Y.; FREITAS, P. M.; CARRARO, L. R.; SAMOWSKI, E. V.; SILA, N.; BATISTA, L. A. R.. |
| Cytological analysis on 112 Brazilian accessions of Paspalum showed that 52 were affected by failure of first or second cytokinesis during microsporogenesis. When the failure of cytokinesis occurred only in the first division and in the second division the cytokinesis was normal, a dyad of microspores was formed. In most of them the two cells remained binucleate, but in some a restitutional nucleus was observed. When the first division was normal and the failure of cytokinesis occurred only in the second division, dyads and triads were observed. A restitutional nucleus in one or both cells of the dyad, or in the binucleate cell of the triad was also observed. The percentage of dyads and triads varied among accessions, reaching 15.75 of the sporads in some.... |
| Tipo: Artigo de periódico |
Palavras-chave: Cytikinesis; 2n gametes; Polyploid; Paspalum; Microsporogenesis. |
| Ano: 1999 |
URL: http://www.alice.cnptia.embrapa.br/alice/handle/doc/44723 |
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| PAGLIARINI, M. S.; VALLE, C. B. do; SANTOS, E. M.; MENDES, D. V.; BERNARDO, Z. H.; MENDES-BONATO, A. B.; SILVA, N.; CALISTO, V.. |
| The genus Brachiaria comprises more than 100 species and is the single most important genus of forage grass in the tropics. Brachiaria brizantha , widely used in Brazilian pastures for beef and dairy production, is native to tropical Africa. As a subsidy to the breeding program underway in Brazil, cytological studies were employed to determine the chromosome number and to evaluate microsporogenesis in 46 accessions of this species available at Embrapa Beef Cattle (Brazil). |
| Tipo: Artigo de periódico |
Palavras-chave: Forage grass.; Pastagem; Brachiaria Brizantha.; Microsporogenesis; Breeding.. |
| Ano: 2012 |
URL: http://www.alice.cnptia.embrapa.br/alice/handle/doc/937123 |
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| Santos,Lídia Márcia Silva; Pereira,Telma Nair Santana; Souza,Margarete Magalhães de; Damasceno Junior,Pedro Correa; Costa,Fabiane Rabelo da; Ribeiro,Beatriz Ferreira; Freitas,Noil Gomes de; Pereira,Messias Gonzaga. |
| The objective of this study was to describe the pollen grain development in hermaphrodite papaya tree. The flower buds were collected at different stages of the development and the anthers were treated chemically for observation under optical and electronic transmission microscopes. The pollen grain development followed the normal pattern described for the Angiosperms. The pollen grain development was described from meiocyte to the mature pollen grain. In the microsporogenesis, the microspore mother cells or the meiocytes underwent meiosis giving rise to the tetrads that were enclosed by the calose. Later, the tetrads were released by the dissolution of the calose by calase activity and microspores underwent mitosis. Microgametogenesis was characterized by... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Carica papaya; Microsporogenesis; Microgametogenesis; Pollen grain; Ultrastructure. |
| Ano: 2008 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132008000300013 |
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| Souza,Margarete Magalhães; Martins,Ernane Ronie; Pereira,Telma Nair Santana; Oliveira,Luiz Orlando de. |
| The aim of this work was to carry out the reproductive studies on Brazilian accessions of ipecac, Psychotria ipecacuanha. It presented heterostyly, with brevistylous and longistylous flowers. The pollen development was observed from the sections of the anthers embedded in resin. Anther development was normal as usually observed in dicotyledones, displaying four layers: outer epidermis, endothecium, middle layer and inner tapetum. The pollen was bicellular and filled with starch at the microspore stage. Pollen morphology was studied using SEM, which showed pollen polymorphism within and between the two floral morphs. Five types of pollen with reticulate or perforate exine were identified. The characteristics showed that the sexual process was as important... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Ipecac; Heterostyly; Anther anatomy; Microsporogenesis; Exine. |
| Ano: 2008 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132008000500015 |
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| Registros recuperados: 16 | |
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