Ultrastructure and Biology of Female Gametophyte in Flowering Plants

Kapil, R. N.; Bhatnagar, A. K.

doi:10.1016/s0074-7696(08)61134-1

Cited by 58 publications

(41 citation statements)

References 77 publications

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“…In several angiosperms, the speed with which the cell walls are formed after the last mitotic cycle makes it difficult to follow step by step the cellularization process. This has been pointed as a cause of the lack of information about that critical ontogenetic stage of the female gametophyte (Kapil & Bhatnagar 1981, Bhandari & Chitralekha 1989. In contrast with the observation of Bhandari & Chitralekha (1989) for Ranunculus sceleratus, during cellularization of the megagametophyte of Tabebuia pulcherrima the cell plates are not PAS-positive.…”

Section: Discussionmentioning

confidence: 96%

“…The polar nuclei are quite voluminous with prominent nucleoli, containing nucleolar vacuoles. Such characters are ordinarily observed in the central cell of most of the angiosperms (Kapil & Bhatnagar 1981, Willemse & van Went 1984, Huang & Russell 1992 and they indicate an intense metabolic activity, obviously associated with the function of the central cell as progenitor of the endosperm. Preliminary observations of the fertilization process reveal that the fusion of the polar nuclei occurs only after the pollen tube reaches the embryo sac.…”

Section: Discussionmentioning

confidence: 99%

“…In this last case, only the plasmalemma delimits the cells (Cocucci & Jensen 1969, Jensen 1972, Kapil & Bhatnagar 1981, Willemse & van Went 1984, Folsom & Cass 1990, Mansfield et al 1991, Russell 1992, Huang & Russell 1992. The total or partial absence of cell walls in the chalazal portion of the egg apparatus is important for double fertilization, as the male gametes released by the pollen tube inside one of the synergids need to be transferred, one to the egg cell and another to the central cell.…”

Section: Discussionmentioning

confidence: 99%

“…With the exception of Plumbago and other genera of the Plumbaginoideae, with no synergids in the embryo sac, in angiosperms the pollen tube penetrates one of the synergids -usually the one that started to undergo a degenerative process -through the filiform apparatus (Schulz & Jensen 1968, Jensen 1972, Kapil & Bhatnagar 1981, Willense & van Went 1984. In Tabebuia pulcherrima the egg cell assumes a lateral disposition and is slightly chalazal in relation to the synergids; consequently it does not establish direct contact with the micropylar channel.…”

Section: Discussionmentioning

confidence: 99%

“…However, details about nuclear migration during the free-nuclear stages of the embryo sac, expansion and organization of its vacuome, and the process of cellularization have received less attention (Kapil & Bhatnagar 1981, Cass et al 1985, Bhandari & Chitralekha 1989. According to Newcomb (1973) and Kapil & Bhatnagar (1981), the scarcity of this kind of information may be due to the difficulty to collect suitable material at critical stages. But the study of these aspects of embryo sac development, in several particular cases, is essential for a more comprehensive understanding of structural and functional organization of the mature megagametophyte.…”

Section: Introductionmentioning

confidence: 99%

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Ovule ontogeny of Tabebuia pulcherrima Sandwith (Bignoniaceae): embryo sac development

Bittencourt¹,

Mariath²

2002

Rev. bras. Bot.

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-(Ovule ontogeny of Tabebuia pulcherrima Sandwith (Bignoniaceae): embryo sac development). The chalazal megaspore develops in a Polygonum-type embryo sac. The amyloplast-rich endothelium is partially degraded during the expansion of the micropylar portion of the megagametophyte. Organization of the mature embryo sac is determined by the patterns of vacuolation, nuclear migration, spindle orientation and cellularization. The egg cell is slightly chalazal in relation to the synergids, and its micropylar end does not touch the micropylar channel. At the chalazal pole of the egg apparatus, the common walls between the synergids, the egg and central cells, despite their tenuity, are present in the mature megagametophyte. The polar nuclei do not fuse before fertilization and the antipodals are persistent until the first stages of endosperm formation. The taxonomic significance of some embryological characters for the Bignoniaceae is discussed.RESUMO -(Ontogenia do óvulo de Tabebuia pulcherrima Sandwith (Bignoniaceae): desenvolvimento do saco embrionário). O megásporo calazal origina um saco embrionário tipo Polygonum. O endotélio rico em amiloplastos é parcialmente degradado durante a expansão da porção micropilar do megagametófito. A organização do saco embrionário maduro é determinada pelos padrões de vacuolação, migração nuclear, orientação dos fusos mitóticos e celularização. A oosfera é ligeiramente calazal em relação às sinérgides e sua extremidade micropilar não estabelece contato com o canal micropilar. Na porção calazal do aparato oosférico, as paredes comuns entre as sinérgides, a oosfera e a célula média, embora muito tênues, estão presentes no saco embrionário maduro. Os núcleos polares não se fundem antes da fecundação e as antípodas persistem até o início do desenvolvimento do endosperma. O significado taxonômico de alguns caracteres embriológicos para a família Bignoniaceae é discutido.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Ovule ontogeny of Tabebuia pulcherrima Sandwith (Bignoniaceae): embryo sac development

Bittencourt¹,

Mariath²

2002

Rev. bras. Bot.

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Postpollination Flower Development

O’Neill

Nadeau²

1996

Horticultural Reviews

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Embryology of Calypso Bulbosa. I. Ovule Development

Law

Yeung

1989

American J of Botany

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Calypso bulbosa is a terrestrial orchid that grows in north temperate regions. Like many orchids, the Calypso has ovules that are not fully developed at anthesis. After pollination, the ovule primordia divide several times to produce a nucellar filament which consists of five to six cells. The subterminal cell of the nucellar filament enlarges to become the archesporial cell. Through further enlargement and elongation, the archesporial cell becomes the megasporocyte. An unequal dyad results from the first meiotic division. A triad of one active chalazal megaspore and two inactive micropylar megaspores are the end products of meiotic division. Callose is present in the cell wall of the megaspore destined to degenerate. In the mature embryo sac the number of nuclei is reduced to six when the chalazal nuclei fail to divide after the first mitotic division. The chalazal nuclei join the polar nucleus and the male nucleus near the center of the embryo sac subsequent to fertilization.

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Ultrastructure and Biology of Female Gametophyte in Flowering Plants

Cited by 58 publications

References 77 publications

Ovule ontogeny of Tabebuia pulcherrima Sandwith (Bignoniaceae): embryo sac development

Ovule ontogeny of Tabebuia pulcherrima Sandwith (Bignoniaceae): embryo sac development

Postpollination Flower Development

Embryology of Calypso Bulbosa. I. Ovule Development

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