Chapter 4: Pollination - Notes

Chapter 4: Pollination - Notes

1. Flower: Introduction

  • Function: Reproductive organ of flowering plants. Produces seeds → seeds grow into new plants.
  • Purpose: Flowers make seeds. Seeds are inside fruits.
  • Support: Flower is attached to stem/stalk called Pedicel. Swollen end of pedicel = Thalamus.

2. Parts of a Flower

A flower has 4 main whorls arranged on the thalamus:

Whorl Name Description Function
1st, Outermost Calyx Made of green, leaf-like Sepals Protects flower in bud stage; can make food
2nd Corolla Made of brightly coloured Petals Attract insects with colour/scent for pollination
3rd Androecium Male part. Collection of Stamens Stamen = Filament + Anther. Anther makes pollen grains (male gametes)
4th, Innermost Gynoecium Female part. Collection of Carpels/Pistils Pistil = Stigma + Style + Ovary. Ovary has ovules (female gametes)
Infobuzz:
  1. Saffron = expensive spice from crocus flower.
  2. Pollen is usually yellow, but can be red, purple, brown, white too.

3. Types of Flowers

Based on reproductive parts present:

  1. Bisexual Flowers: Have both stamen + pistil. Has all 4 whorls.
    Ex: Hibiscus, tulip, rose, lily
  2. Monosexual Flowers: Have only one reproductive part.
    • Male flowers: Only stamens
    • Female flowers: Only pistils
    Ex: Watermelon, pumpkin, cucumber, papaya

4. Pollination

Definition: Transfer of pollen grains from anther to stigma.

Importance: Essential for seed production. Fusion of male gamete (pollen) + female gamete (ovule) = seed.

Agents of Pollination: Insects, birds, animals, wind, water.
Ex: Pollination by bee, butterfly, hummingbird.

5. Process of Pollination

  1. Male gametes are in pollen grains inside anther.
  2. When anthers mature, they split open and release pollen.
  3. Female gametes are in ovules inside ovary.
  4. Pollen must reach stigma to travel down the style to ovary for fertilization.

6. Ways of Pollination

Type Definition Needs Agents? Examples
Self-Pollination Pollen from anther → stigma of same flower or another flower on same plant No carriers needed Peanuts, orchids, peas
Cross-Pollination Pollen from anther of one flower → stigma of another flower on different plant of same kind Needs agents: insects, wind, water, birds Apples, maples, tulips

7. Activities - Hibiscus Flower Study

  1. Sepals: Outermost green layer. Protects bud.
  2. Petals: Large, red, coloured. Attract insects.
  3. Stamen: Male part. Filament = thread-like stalk. Anther = kidney-shaped tip, produces pollen.
  4. Pistil: Female part. Stigma = sticky top to catch pollen. Style = tube connecting stigma to ovary. Ovary = swollen base, contains ovules. After fertilization, ovary → fruit, ovules → seeds.

Quick Revision Keywords

Pedicel, Thalamus, Sepals, Petals, Stamen, Anther, Filament, Pollen grains, Pistil, Stigma, Style, Ovary, Ovule, Bisexual, Monosexual, Self-pollination, Cross-pollination, Agents.