Lesson 8 of 12 · 10 min
Double fertilisation
NCERT §1.3
One pollen tube delivers two male gametes into a paddy ovule. Both are used, one to make the embryo and one to make its food. What chromosome numbers result?
The lesson in notes
In short
Inside the synergid the pollen tube releases its two male gametes into the synergid's cytoplasm.
One male gamete fuses with the egg nucleus: this is syngamy, and it gives a diploid zygote.
The other male gamete fuses with the two polar nuclei in the central cell, giving a triploid primary endosperm nucleus (PEN). Because three haploid nuclei fuse, this is called triple fusion.
Two fusions, syngamy and triple fusion, in one embryo sac make up double fertilisation, an event unique to flowering plants.
After triple fusion the central cell becomes the primary endosperm cell (PEC), which develops into the endosperm; the zygote develops into the embryo.