Double fertilisation (syngamy + triple fusion)दोहरा निषेचन (युग्मक संलयन + त्रिसंलयन)

NCERT Fig 1.12e, 1.13a · Class 12 Biology · Chapter 1 · interactive diagram

Parts and their functions

• Pollen tube (पराग नलिका) — Enters one synergid and releases the two male gametes into its cytoplasm.
• Male gametes (2) (नर युग्मक (2)) — One moves to the egg (syngamy); the other moves to the two polar nuclei in the central cell (triple fusion).
• Egg cell (n) (अंड (n)) — Fuses with one male gamete — SYNGAMY.
• Zygote (2n) (युग्मनज (2n)) — Diploid cell formed by syngamy; develops into the embryo.
• Polar nuclei (ध्रुवीय केंद्रक) — Two haploid nuclei in the central cell.
• Primary endosperm nucleus (PEN, 3n) (प्राथमिक भ्रूणपोष केंद्रक (3n)) — Male gamete + 2 polar nuclei: fusion of THREE haploid nuclei = TRIPLE FUSION → triploid PEN. The central cell becomes the primary endosperm cell (PEC) and develops into the endosperm.
• Central cell → primary endosperm cell (PEC) (केंद्रीय कोशिका → प्राथमिक भ्रूणपोष कोशिका) — After triple fusion the central cell becomes the PEC, which develops into the endosperm.
• Synergid (सहायक कोशिका) — The pollen tube enters one synergid through the filiform apparatus.
• Antipodals (प्रतिमुख कोशिकाएँ) — Three cells at the chalazal end; they degenerate after fertilisation.

Steps

1. The pollen tube carrying 2 male gametes reaches the embryo sac.
2. It enters a synergid (via the filiform apparatus) and releases both male gametes.
3. One gamete → egg (SYNGAMY). The other → 2 polar nuclei (TRIPLE FUSION).
4. Result: zygote (2n) → embryo, and PEN (3n) → endosperm. Two fusions in one embryo sac = DOUBLE FERTILISATION, unique to flowering plants.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 1.12e, 1.13a. Report a mistake