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The Female Reproductive Apparatus

Master the structure of the ovule and the precise cellular layout of the 7-celled, 8-nucleate female gametophyte.

6 lessons

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The Rule of One

Out of the four megaspores created by meiosis, three degenerate and die. Only one functional megaspore survives to form the entire female gametophyte (embryo sac). This is known as monosporic development.

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The Ovule (Megasporangium)

Structure of the pistil and the internal anatomy of an ovule.

The Pistil: Female Reproductive Hub

The gynoecium represents the female reproductive part of the flower, consisting of the pistil. Each pistil has three parts: the stigma (landing pad for pollen), style (elongated stalk), and ovary (basal bulged part).

Pistils can be syncarpous (fused together) or apocarpous (free).

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Anatomy of an Ovule

Diagram of an anatropous ovule.

clean scientific diagram, pastel color palette, elegant typography, precise labeling, translucent layers for cross-sections, white background, soft shadows showing a typical anatropous ovule with labels for Hilum, Funicle, Micropyle, Micropylar pole, Outer integument, Inner integument, Nucellus, Embryo sac, and Chalazal pole

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(a) A dissected flower of Hibiscus showing pistil (other floral parts have been removed)

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(b) Multicarpellary, syncarpous pistil of Papaver

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(c) A multicarpellary, apocarpous gynoecium of Michelia;

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(d) A diagrammatic view of a typical anatropous ovule - with Hilum, Funicle, Micropyle, Micropylar pole, Outer integument, Inner integument, Nucellus, Embryo sac, and Chalazal pole

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Megasporogenesis & Embryo Sac Formation

How a single megaspore becomes a 7-celled, 8-nucleate structure.

From Cell to Embryo Sac

The process starts with a single large cell in the nucellus called the Megaspore Mother Cell (MMC).

The MMC undergoes meiosis to produce four megaspores. In most flowering plants, three degenerate and only one remains functional.

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The Mature Embryo Sac

Distribution of the 7 cells and 8 nuclei inside the embryo sac.

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(a) Parts of the ovule showing a large megaspore mother cell, a dyad and a tetrad of megaspores.

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(b) 2, 4, and 8-nucleate stages of embryo sac and a mature embryo sac;

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(c) A diagrammatic representation of the mature embryo sac.

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Map the Embryo Sac

Match the cells of the embryo sac to their locations and features.

NoteMatch each part of the embryo sac to its correct location and description.

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Terms

Definitions