⚡ Quick Revision: Structure of a Bisexual Flower
The Four Whorls
- ✔ Calyx (Sepals): Outermost green whorl; protects the flower in the bud stage.
- ✔ Corolla (Petals): Brightly colored to attract pollinators like insects and birds.
- ✔ Androecium & Gynoecium: The essential whorls directly involved in reproduction.
Longitudinal Section (L.S.) of a Flower
Term Card
Thalamus (Receptacle): The enlarged end of the flower stalk (pedicel) on which all four whorls are arranged.
❌ Don't Confuse:
Bracts with Sepals. Bracts are leaf-like structures at the base of the flower stalk, whereas sepals are part of the flower itself.
⚡ Quick Revision: The Essential Whorls
1. Androecium (Male Part)
- ✔ Composed of Stamens; each stamen consists of a long Filament and an Anther.
- ✔ The anther produces Pollen Grains which contain the male gametes.
- ✔ Stamens may be free (Polyandrous) or fused in groups (Monadelphous, Diadelphous).
2. Gynoecium (Female Part)
- ✔ Composed of Carpels (Pistils); each carpel has a Stigma, Style, and Ovary.
- ✔ The Ovary contains Ovules, which develop into seeds after fertilization.
- ✔ The Stigma is the terminal sticky part that receives pollen grains.
Term Card
Placentation: The arrangement of ovules inside the ovary (e.g., Marginal, Axile, Parietal).
❌ Don't Confuse:
Androecium with Gynoecium. Just remember: Andro refers to male, Gyno refers to female (like in 'Gynaecologist').
⚡ Quick Revision: Types of Flowers & Inflorescence
| Type of Flower | Key Characteristic | Example |
|---|---|---|
| Complete | All 4 whorls present. | Hibiscus, Pea |
| Incomplete | One or more whorls missing. | Papaya, Date palm |
| Bisexual | Both stamens and carpels present. | Rose, Lily |
| Unisexual | Either only male or only female. | Cucumber, Maize |
Inflorescence & Special Terms
- ✔ Inflorescence: The mode of arrangement of flowers on the axis (peduncle).
- ✔ Perianth: When Calyx and Corolla are not distinct (e.g., in Onion, Lily). Individual units are called Tepals.
- ✔ Nectaries: Groups of nectar-secreting cells usually at the base of the ovary or petals.
Term Card
Neuter Flower: A flower which lacks both stamens and carpels (e.g., ray florets of Sunflower).
❌ Don't Confuse:
Monoecious with Dioecious. Monoecious plants have male and female flowers on the same plant (e.g., Maize). Dioecious plants have them on separate plants (e.g., Papaya).