Angiosperms: An Introduction to Fruits

Key Concepts

• Angiosperms: Two defining features are flowers and fruits.
• Fruits: Mature ovaries from the carpal of the flower.
  • Develop from the ovary wall after fertilization.
  • Contain seeds, endosperm, and seed coat.

Anatomy of a Fruit

• Ovary Wall Layers:
  • Exocarp: Outer layer
  • Mesocarp: Middle layer
  • Endocarp: Inner layer
• Fruit Development: Ovary wall ripens into the fruit.

Types of Fruits

Simple Fruits

• Develop from one ovary of one flower.
• Types:
  • Follicles: One ovary chamber, dry, bursts to release seeds.
  • Pods: One ovary with multiple seeds (e.g., legumes like peas).
  • Droops: Hardened endocarp around the seed (e.g., stone fruits like peaches).
  • Acheans: Entire ovary wall hardened (e.g., sunflower seeds).
  • Berries: Fleshy ovary wall with seeds, often with multiple chambers (e.g., tomatoes, oranges).

Aggregate Fruits

• Multiple ovaries from one flower.
• Example: Strawberries, raspberries, blackberries.

Multiple Fruits

• Multiple flowers fuse during maturation.
• Examples: Pineapples, figs.

Accessory Fruits

• Contain other flower parts besides the ovary.
• Examples: Apples (pomes), strawberries.

Fruit Function

• Seed Dispersal: Essential for spreading embryos away from the parent plant.
• Dispersal Methods:
  • Water: e.g., coconuts carried by ocean currents.
  • Wind: Lightweight, with structures to catch the wind (e.g., dandelion umbrellas).
  • Animals:
    • Hitchhiking: e.g., burrs attach to animal fur.
    • Food for Dispersal: Fruits eaten by animals, seeds dispersed in droppings (e.g., bears and berries).
    • Storage by animals: e.g., squirrels burying acorns.

Angiosperm Life Cycle

• Sporophyte: Produces flowers made of sporophylls.
• Carpal: Female portion of the flower.
  • Contains ovary with ovules.
  • Fertilization: Leads to seed and fruit development.
• Stamens: Male portion of the flower.
  • Contains anther with microsporangium.
  • Pollen grains develop and land on stigma for fertilization.
• Double Fertilization:
  • Involves two sperm cells.
• Post-Fertilization:
  • Ovule becomes seed.
  • Ovary becomes fruit for seed dispersal.

Conclusion

• Flowers: Aid in pollen dispersal.
• Fruits: Facilitate embryo dispersal.

These notes summarize the key points about the development and types of fruits, their role in the life cycle of angiosperms, and their methods of seed dispersal.