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#female gametophyte

6 public questions tagged with this topic.

plant Development - 1

Embryo sac consists of:

Embryo sac in Polygonum-type typical of approximately seventy percent angiosperms consists of seven cells organized around eight nuclei arising from three sequential free nuclear mitoses of functional megaspore without initial cytokinesis. Configuration comprises micropylar egg apparatus with two synergids flanking egg cell, large central cell with two polar nuclei occupying huge central vacuole, and chalazal three antipodal cells often ephemeral. This precise seven-celled eight-nucleate organization positions egg for fertilization, synergids for pollen tube attraction, central cell for endosp

Ref: Drews & Koltunow, Arabidopsis Book 2011: typical embryo sac seven cells eight nuclei Polygonum-type organization.

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plant Development - 1

Megasporogenesis results in formation of:

Megasporogenesis occurs within ovule nucellus where subepidermal archesporial cell enlarges into megaspore mother cell undergoing meiosis I and II producing linear tetrad of four haploid megaspores with distinct animal-vegetal polarity. Three megaspores positioned toward micropyle undergo programmed cell death degenerating completely, while chalazal-most megaspore located near nutrient supply survives as functional megaspore. This selective survival establishes female germline lineage. Functional megaspore subsequently undergoes megagametogenesis involving three consecutive free nuclear mitose

Ref: Reiser & Fischer, Plant Cell 1993; Yadegari & Drews: megasporogenesis yields one large functional megaspore, three degenerate.

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Plant Classification

Which structure protects the female gametophyte in seed plants?

Female gametophyte deeply embedded protected by diploid nucellus megasporangium and surrounding one or two integuments forming ovule; integuments leave micropyle opening for pollen entry but otherwise seal gametophyte from desiccation pathogens UV. Antheridium protects male gametes in bryophytes pteridophytes jacked cells, archegonium encloses egg within neck jacket cells venter, spore wall protects dispersed spore not retained gametophyte itself after meiosis. Ovule evolution considered key innovation enabling seed plants to colonize dry habitats by eliminating free-living delicate female gam

Ref: NCERT Class 12 Biology, Chapter 2: Ovule integuments protection female gametophyte function

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Plant Classification

Female gametophyte of angiosperms typically consists of

Typical angiosperm embryo sac follows Polygonum development: megaspore mother cell meiosis yields functional chalazal megaspore, three mitoses without cytokinesis create eight free nuclei, cellularization partitions them into seven cells. At micropylar pole egg apparatus includes single egg flanked by two synergids secreting LURE chemoattractants guiding pollen tube via filiform apparatus. Chalazal pole bears three antipodals often degenerated or proliferative in cereals. Central region holds central cell containing two polar nuclei awaiting fusion with sperm to form endosperm. This seven-cell

Ref: NCERT Class 12 Biology, Chapter 2: Polygonum type embryo sac 7 cells 8 nuclei structure

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Sexual Reproduction in flowering Plants

A typical angiosperm embryo sac at maturity is described as '7-celled and 8-nucleate'. Which of the following cells are

In the embryo sac, the Egg cell, Synergids, and Antipodals are all derived from the haploid megaspore via mitosis, so they are haploid (n). The Central cell contains two polar nuclei (n+n) before fertilization. The Zygote (2n) and Primary Endosperm Nucleus (3n) are post-fertilization structures.

Ref: Diagram of a mature embryo sac showing the egg apparatus, central cell, and antipodals.

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