Wyniki wyszukiwania

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Ovule, megaspores, and female gametophyte formation in Larix decidua Mill. [Pinaceae]

100%

Slobodnik B., Guttenberger H.

Acta Biologica Cracoviensia. Series Botanica

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2000

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tom 42

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nr 2

Compared to the formation of male generative organs, the development of female sporogenous tissue of the European larch (Larix decidua Mill.) is considerably delayed. The young megaspore mother cell (megasporocyte, MMC) is not observable until late October, a short time before the period of dormancy. In early spring, MMCs become moderately enlarged, with intensive accumulation of starch grains around the nucleus. At the end of the first 10 days of March the MMCs become more rounded in section and the nucleus moves towards the basal part of the cell (near the chalaza). The integument and nucellus become observable at that time and chromosomal strands are visible in the MMC nuclei. Meiosis of MMCs was observed from mid-March to early April. During that period the tip of the integument grows gradually over the nucellus and creates the stigmatic apparatus of the ovule. Instead of the expected tetrads, triads of linearly arranged unequal megaspores were observed in individual ovules at the beginning of pollen shedding. Immediately after meiosis of the MMC, massive growth of the functional chalazal megaspore occurs, along with intensive free-nuclear divisions. The nuclei become located near the megaspore membrane, whereas the whole central part of the developing female gametophyte is filled with an extraordinarily large central vacuole. During intensive growth of the functional megaspore, the innermost layer of the nucellar tapetum gradually disintegrates. This development stage lasts until early May, when the megaspore membrane segregates partially from the nucellar tapetum and the free-nucleate female gametophyte assumes an irregular sac-like shape. The cellular stage of the female gametophyte with typical pyramidal cells at its micropylar end is visible at mid-May. Then the vacuolated (so-called frothy) archegonia gradually forms. The disappearance of vacuoles and the division of the central cell were registered in late May. At the stage of the large female gamete (egg cell) and the small ventral canal cell, the archegonia become fully receptive for fertilization. Our observations indicate that the development of the free-nucleate gametophyte and the formation of cell walls among the nuclei are the most sensitive phases of ovule development in the European larch before fertilization. During these stages, numerous cases of degeneration of the female gametophyte were observed, along with the complete deformation of ovules. The reasons for frequent irregularities are discussed here; the influence of meteorological and nutrient conditions seems especially important.

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New species of megaspores from the Trias of Poland

84%

Fuglewicz R.

Acta Palaeontologica Polonica

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1977

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tom 22

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nr 4

Thirty new species and two new genera (Otynisporites, Bothriotriletes) of megaspores from the Trias of Polish Lowlands have been described. Most of them are from the Lower Keuper (Lettenkohle) and the Upper Buntsandstein. The megaspores from the Lower Buntsandstein have been described.

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In vitro embryo sac development via ovule cultures in Doritis pulcherrima

84%

Ye X.-L., Wu C.-H., Liang C.-Y.

Acta Biologica Cracoviensia. Series Botanica. Supplement

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2005

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tom 47

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nr 1

4

Ovule, megaspores, and female gametophyte formation in Larix decidua Mill.

84%

Slobodnik B.

Acta Biologica Cracoviensia. Series Botanica. Supplement

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1999

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tom 41

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nr 1

5

Development of generative organs in pepino [Solanum muricatum Ait]

84%

Kopcinska J., Lotocka B., Kowalczyk K., Kobryn J.

Acta Biologica Cracoviensia. Series Botanica. Supplement

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1999

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tom 41

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nr 1

6

Structural and biochemical changes in the micropylar region of Chondrilla juncea apomictic ovule

67%

Koscinska-Pajak M., Chudzik B., Zarzyka B., Pawelec J.

Acta Biologica Cracoviensia. Series Botanica. Supplement

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2005

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tom 47

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nr 1

Ograniczanie wyników

4 Acta Biologica Cracoviensia. Series Botanica. Supplement

1 Acta Biologica Cracoviensia. Series Botanica

1 Acta Palaeontologica Polonica

2 Slobodnik B.

1 Chudzik B.

1 Fuglewicz R.

1 Guttenberger H.

1 Kobryn J.

1 Kopcinska J.

1 Koscinska-Pajak M.

1 Kowalczyk K.

1 Liang C.-Y.

1 Lotocka B.

1 Pawelec J.

1 Wu C.-H.

1 Ye X.-L.

1 Zarzyka B.

2 2005

1 2000

2 1999

1 1977

Ovule, megaspores, and female gametophyte formation in Larix decidua Mill. [Pinaceae]

New species of megaspores from the Trias of Poland

In vitro embryo sac development via ovule cultures in Doritis pulcherrima

Ovule, megaspores, and female gametophyte formation in Larix decidua Mill.

Development of generative organs in pepino [Solanum muricatum Ait]

Structural and biochemical changes in the micropylar region of Chondrilla juncea apomictic ovule