Critical Ploidy Values
| Structure | Origin | Ploidy | Chromosome Number (if 2n=14) |
|---|---|---|---|
| PMC (pollen mother cell) | Sporophyte | 2n | 14 |
| Microspore / Pollen grain | From PMC by meiosis | n | 7 |
| Vegetative nucleus | In pollen grain | n | 7 |
| Generative cell | In pollen grain | n | 7 |
| Sperm cell | From generative cell (mitosis) | n | 7 |
| MMC (megaspore mother cell) | Sporophyte | 2n | 14 |
| Functional megaspore | From MMC by meiosis | n | 7 |
| Egg cell | In embryo sac | n | 7 |
| Polar nuclei (each) | In central cell | n | 7 |
| Synergids | In embryo sac | n | 7 |
| Antipodals | In embryo sac | n | 7 |
| Zygote | Sperm + egg (syngamy) | 2n | 14 |
| Primary endosperm nucleus (PEN) | Triple fusion | 3n | 21 |
| Endosperm | From PEN (mitosis) | 3n | 21 |
| Embryo | From zygote (mitosis) | 2n | 14 |
| Seed coat (testa + tegmen) | From integuments (maternal) | 2n | 14 |
| Pericarp | From ovary wall (maternal) | 2n | 14 |
Key Formulas
- Endosperm ploidy = n(sperm) + n(polar1) + n(polar2) = 3n
- Zygote ploidy = n(sperm) + n(egg) = 2n
- Free nuclear divisions in embryo sac = 3 (produces 8 nuclei from 1 megaspore: 1→2→4→8)
- Microspore tetrad = 4 cells from 1 PMC (meiosis)