Angiosperms — Defining Features:
- Seeds ENCLOSED in fruits (ovary wall → fruit)
- Flowers — co-evolved with pollinators
- Double fertilization (EXCLUSIVE feature):
- Sperm 1 + Egg → Zygote (2n) → Embryo
- Sperm 2 + 2 Polar nuclei → Primary Endosperm Nucleus (3n) → Endosperm
- Female gametophyte = 7-celled embryo sac (3 antipodals + 2 synergids + 1 egg + 1 central cell with 2 polar nuclei = 8 nuclei)
- Most diverse plant group (~300,000 species; ~90% of all land plants)
Monocotyledons vs Dicotyledons:
| Feature | Monocot | Dicot |
|---|---|---|
| Cotyledons | 1 | 2 |
| Leaf venation | Parallel | Reticulate |
| Root system | Fibrous (adventitious) | Tap root |
| Vascular bundles | Scattered, closed (no cambium) | Ring, open (cambium present) |
| Floral symmetry | Trimerous (×3) | Tetramerous (×4) or Pentamerous (×5) |
| Secondary growth | Absent | Present |
| Pollen | Monosulcate (1 aperture) | Tricolpate (3 apertures) |
| Examples | Rice, Wheat, Maize, Lily, Onion | Mango, Pea, Rose, Sunflower, Neem |
NEET Critical Points:
- Double fertilization → ANGIOSPERMS ONLY
- Endosperm = TRIPLOID (3n) — sperm (n) + two polar nuclei (n + n = 2n) = 3n
- Monocot VB = scattered + closed (NO cambium = NO secondary growth)
- Dicot VB = ring + open (cambium present = secondary growth = wood)