Megasporogenesis

• During the development of ovule, in the beginning of this process, nucellus develops form the placenta in the form of a small rounded out growth like structure.
• At this stage, all the cells of nucellus are undifferentiated, homogenous and meristematic. This mass of cells surrounded by single celled thick layer of epidermis.
• Any one hypodermal cell of nucellus is differentiated and increase in size. It becomes different from rest of the cells due to presence of…

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Development of Embryosac or Female Gametophyte

• Megagametogenesis: Megaspore is the first cell of the female gametophyte. This megaspore grows in size and obtains nutrition from the nucellus.
• The nucleus of megaspore divides mitotically to form two nuclei. Each nucleus moves towards the opposite pole and reached at their respective poles.
• Both the nuclei lie at poles divide twice mitotically. Resulting, four-four nuclei are formed at each pole (Total 8-nuclei).
• Out of the four, one-one nucleus migrates from …

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Type of Embryo Sacs

Mainly embryo sacs are three types;

• Monosporic Embryosac: When only one megaspore nucleus forms the embryo sac, the development is monosporic. It is two types:
  • Polygonum type: The polygonum type of embryo sac was first observed in Polygonum divaricatum by Strasburger in 1879. It is eight nucleate and seven celled. As a result of megasporogenesis, a megaspore tetrad is formed and out of these, chalazal megaspore is functional and undergoes to three simultaneous…

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