4.1 Pollination

Key Concepts: Detailed Parts of a Flower

• Vegetative Parts:
  • Peduncle: Flower stalk.
  • Receptacle: Where flower parts attach.
  • Sepals (Calyx): Protect bud.
  • Petals (Corolla): Attract pollinators.
• Reproductive Parts:
  • Stamen (Androecium): Male (anther produces pollen, filament supports).
  • Pistil/Carpel (Gynoecium): Female (stigma receives pollen, style connects, ovary contains ovules).

Detailed Pollination Process

1. Pollen Transfer: Pollen moves from anther to stigma.
2. Pollen Germination: Pollen grain lands on stigma, absorbs nutrients, grows a pollen tube down the style.
3. Fertilization: Pollen tube carries male gametes to meet female gamete (egg) inside ovule; fusion occurs.
4. Seed and Fruit Development: Ovule develops into seed, ovary into fruit.

Types of Pollination

1. Self-Pollination: Pollen transferred within the same flower or to another flower on the same plant.
   • Autogamy: Same flower (e.g., peas).
   • Geitonogamy: Another flower on same plant (e.g., maize).
2. Cross-Pollination (Xenogamy): Pollen transferred from one plant to another plant of the same species.
   • Increases genetic diversity.

Agents of Cross-Pollination

• Biotic Agents (Zoophily): Animals.
  • Entomophily (Insects): Bees, butterflies (bright, fragrant flowers, nectar).
  • Ornithophily (Birds): Hummingbirds (bright, tubular flowers, large nectar).
  • Chiropterophily (Bats).
• Abiotic Agents: Non-living factors.
  • Anemophily (Wind): Small, less showy flowers; light, dry pollen (e.g., maize, paddy).
  • Hydrophily (Water): Less common; pollen carried by water.

Bisexual and Unisexual Flowers

• Bisexual Flowers (Hermaphroditic/Complete): Possess both male (stamens) and female (carpels) parts.
  • Examples: Lily, Rose, Sunflower.
• Unisexual Flowers (Incomplete): Contain either stamens or carpels, but not both.
  • Examples: Papaya, Cucumber, Watermelon.
  • Require cross-pollination.

Importance of Pollination

For Food Production

• Crop Yields: Pollinators essential for over 75% of flowering plants, including many food crops.
• Economic Value: Billions of dollars annually to global economy.
• Dietary Diversity: Provides micronutrients and vitamins.

For Biodiversity

• Ecosystem Health: Critical for maintaining biodiversity; over 80% of wild flowering plants pollinated by animals.
• Plant Reproduction and Genetic Diversity: Ensures reproduction and genetic diversity for adaptation.
• Habitat and Food for Wildlife: Supports ecosystem resilience.