Double fertilization is found in

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  1. Male gametophyte – 

    • In an angiosperm, the male gametophyte is represented by a pollen.
    • Each pollen has two male gametes and are carried to the pistil by various pollinating agents.
    • The pollen lands on the stigma and there is a chemical interaction between the pollen and the stigma to determine self-compatibility.
    • When the compatible pollens are recognized, the pollen tube grows towards the ovule carrying the male gametes.

    Female gametophyte – 

    • The female gametophyte is represented by the embryo sac which is 8-nucleate and 7-celled at maturity.
    • It consists of the following cells:
      • Antipodal cells – There are 3 of these uninucleate cells present at the chalazal end that degenerate after fertilization.
      • Central cell – It is centrally located covering most of the embryo sac and contains 2 polar nuclei.
      • Egg cell – It is the female gamete that undergoes fusion with a male gamete.
      • Synergid cells – There are 2 synergid cells at the micropylar end with the filiform apparatus at their base.

    Important Points

    • Double fertilization is a unique characteristic of angiosperms.
    • In this reproductive process, two fertilization processes take place for each embryo sac (female gametophyte).
    • It involves the following 2 processes:
      • Syngamy – It is the fusion of one male gamete with the egg cell to produce a zygote that later develops into embryo.
      • Triple fusion – It is the fusion of the 2nd male gamete with the 2 polar nuclei of the embryo sac to produce the endosperm.

    Therefore, double fertilization can be summed up as:
    1st Male gamete (n) + Egg (n)  →  Zygote (2n)
    2nd Male gamete (n) + 2 Polar nuclei (n)  →  Endosperm (3n)

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