The Flower
Basic Chapter Notes
1.0 Introduction to Flowering Plants
Plants are broadly classified based on their ability to produce flowers:
- Flowering Plants: Produce flowers, seeds, and fruits (e.g., Apple, Mango, Tomato).
- Non-flowering Plants: Do not produce flowers, seeds, or fruits (e.g., Ferns, Mosses).
Definition: Flowers are the brightly coloured parts of a plant involved in the formation of fruits and reproduction.
2.0 Structure of a Flower
A typical flower consists of four main parts (whorls):
1. Calyx (Sepals)
Small, green leaf-like structures at the base. They protect the flower during the bud stage.
Small, green leaf-like structures at the base. They protect the flower during the bud stage.
2. Corolla (Petals)
Brightly coloured parts that attract insects for pollination.
Brightly coloured parts that attract insects for pollination.
3. Androecium (Male Part)
Composed of Stamens. Each stamen has an Anther (contains pollen grains) and a Filament.
Composed of Stamens. Each stamen has an Anther (contains pollen grains) and a Filament.
4. Gynoecium (Female Part)
Composed of Carpels/Pistils. Each carpel has a Stigma, Style, and Ovary.
Composed of Carpels/Pistils. Each carpel has a Stigma, Style, and Ovary.
3.0 Classification of Flowers
- Bisexual Flowers: Have both male (androecium) and female (gynoecium) parts (e.g., Rose, Lily).
- Unisexual Flowers: Have either male or female parts (e.g., Papaya, Watermelon).
4.0 Pollination & Fertilization
Pollination: The transfer of pollen grains from the anther to the stigma.
Fertilization: The process of fusion of the male and female gametes.
Path: Pollen lands on Stigma → Pollen tube grows through Style → Male cell reaches Ovary → Fuses with Egg in Ovule.
Post-Fertilization Changes:
- ✅ Ovary develops into the Fruit.
- ✅ Ovules develop into Seeds.
5.0 Fruit & Seed Structure
Fruit Parts (Pericarp):
- Epicarp: Outer leathery skin.
- Mesocarp: Sweet, fleshy middle part.
- Endocarp: Innermost hard layer containing the seed.
Seed Structure:
- Seed Coat: Consists of outer Testa and inner Tegmen.
- Micropyle: Small pore for water absorption and gas exchange.
- Embryo: Consists of Radicle (future root) and Plumule (future shoot).
6.0 Seed Germination
Germination: The process where the embryo starts to grow using seed reserves.
Conditions Necessary for Germination:
- Water: To rupture the seed coat and activate biochemical reactions.
- Suitable Temperature: Ideally between 25°C - 35°C.
- Oxygen: For providing energy through respiration.
Types of Germination:
- Epigeal: Cotyledons are lifted above ground (e.g., Bean, Castor).
- Hypogeal: Cotyledons remain below ground (e.g., Pea, Gram, Maize).
- Viviparous: Seed germinates while still attached to the parent plant (e.g., Mangroves).