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   Exampix Verified

   2022-08-21T10:17:01+00:00Added an answer on August 21, 2022 at 10:17 am

   Concept:

   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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