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Sexual Reproduction in Flowering Plants
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What is common between vegetative reproduction and apomixis?Vegetative reproduction is asexual reproduction through vegetative parts such as runners, rhizomes, tubers and bulbs.
Apomixis is the production of seeds without fertilisation; it is a form of asexual reproduction that mimics sexual reproduction.
In both, meiosis and syngamy are not involved, so the offspring are genetically identical to the parent (clones).
Apomixis involves flowers and seeds, so it does not bypass the flowering phase; neither process is limited to dicots (apomixis is common in grasses) or occurs round the year.
Hence the common feature is that both produce progeny identical to the parent. -
In angiosperms, functional megaspore develops intoIn the ovule, the megaspore mother cell undergoes meiosis to form four haploid megaspores.
In most flowering plants three of them degenerate and only one remains functional.
The nucleus of the functional megaspore divides mitotically three times (free nuclear divisions) to give 8 nuclei, which organise into the 7-celled, 8-nucleate female gametophyte.
This female gametophyte is the embryo sac; its formation from a single megaspore is called monosporic development.
Endosperm is formed after triple fusion, the pollen sac is the microsporangium, and the ovule is the structure that contains the embryo sac.
Hence the functional megaspore develops into the embryo sac.