1. Microsporogenesis – Flowchart
image ref: uploaded by David Honys
Microsporangium (in anther)
│
▼
Microspore Mother Cell (2n)
│
(Meiosis)
▼
Tetrad of Microspores (n)
│
(Maturation)
▼
Pollen Grains (Male Gametophyte)
│
2 Cells: ➤ Vegetative Cell
➤ Generative Cell (divides → 2 male gametes)
📌 Key Points:
-
Occurs in pollen sacs of the anther.
-
Each microspore mother cell gives rise to 4 microspores.
-
Pollen grains are haploid and unicellular at first.
2. Megasporogenesis – Flowchart
Ovule (in ovary of carpel)
│
Megaspore Mother Cell (2n)
│
(Meiosis)
▼
4 Megaspores (n)
│
(3 degenerate, 1 functional)
▼
Functional Megaspore (n)
│
(3 Mitoses)
▼
Embryo Sac (Female Gametophyte)
│
7 Cells, 8 Nuclei:
➤ 1 Egg Cell
➤ 2 Synergids
➤ 3 Antipodals
➤ 1 Central Cell (with 2 polar nuclei)
📌 Key Points:
-
Only one megaspore becomes functional.
-
Embryo sac is the mature female gametophyte.
Pollination
Transfer of Pollen → Stigma of a Flower
Types:
┌──────────────┬──────────────────────┬───────────────────
Autogamy Geitonogamy Xenogamy (Cross-Pollination)
(Same flower) (Different flower, same plant) (Different plant, same/diff species)
Agents of Pollination
┌──────────┬──────────┬──────────┬──────────┐
│
Wind Insects Water Birds Bats
(Anemophily) (Entomophily) (Hydrophily) (Ornithophily) (Chiropterophily)