Primary endosperm nucleus (PEN) is formed by the fusion of

Primary endosperm nucleus (PEN) is formed by the fusion of
  1. 2 polar nuclei +1 synergid cell nucleus
  2. 1 polar nucleus +1 antipodal cell nucleus +1 synergid cell nucleus
  3. 2 polar nuclei +1 male gamete nucleus
  4. 2 antipodal cell nuclei +1 male gamete nucleus.

Solution

During the event of double fertilisation in angiosperms, the second male gamete fuses with the two haploid polar nuclei or diploid secondary nucleus of the central cell to form a triploid primary endosperm nucleus (PEN). This second fertilisation is called vegetative fertilisation.

Asked in: NEET 2007

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