Pre-Fertilization → Post-Fertilization Transformation Overview
Key Structural Diagrams
Pollen Grain Cross-Section:
[Pollen grain layers: Exine (outer, sporopollenin, highly resistant) → Intine (inner, cellulose + pectin) → Vegetative cell (tube nucleus) → Generative cell (within vegetative cell cytoplasm) → Germ pore (exine-free aperture for pollen tube emergence)]
Layers: Exine (outer, sporopollenin-based) → Intine (inner, cellulose/pectin) → Vegetative cell (with tube nucleus) → Generative cell (smaller, within vegetative cell cytoplasm) → Germ pore (exine-free region)
Embryo Sac Orientation:
The embryo sac (female gametophyte): egg cell + 2 synergids at micropylar end; central cell with 2 polar nuclei; 3 antipodals at chalazal end. Source: Wikimedia Commons (CC BY-SA).
Top = Chalazal end (3 antipodals) → Middle = Central cell (2 polar nuclei) → Bottom = Micropylar end (egg apparatus: egg + 2 synergids) → Micropyle below
Ploidy Summary Diagram
| Structure | Ploidy | Source |
|---|---|---|
| Pollen grain | n | Meiosis of PMC (2n) |
| Egg cell | n | Mitosis from megaspore (n) |
| Zygote | 2n | Syngamy (n+n) |
| PEN/Endosperm | 3n | Triple fusion (n+n+n) |
| Embryo | 2n | Mitosis from zygote |
| Seed coat | 2n | From integuments (maternal 2n) |
| Pericarp | 2n | From ovary wall (maternal 2n) |