Sexual Reproduction in Flowering Plants

Sexual Reproduction in Flowering Plants

• Sexual reproduction involves the fusion of male and female gametes
• Pollen grains are the male gametophytes
• Pollen grains develop from microspores within the anther
• Pollen grains are transported to the stigma of the flower (pollination)
• Microspore mother cells undergo meiosis
• Microspores mature into pollen grains (2n to n)
• Meiosis and Dehydron
• Variable viability of pollen grains varies by species
• Pollination types include:
  • Autogamy (same flower)
  • Geitonogamy (different flowers on the same plant)
  • Xenogamy (different plants)
• Pollination agents can be biotic (e.g., insects, birds) or abiotic (e.g., wind, water)
• Pollen grains are transferred from the anther to the stigma.
• The pollen tube grows through the style to the ovary.
• Double fertilization involves one sperm fertilizing the egg and the other fertilizing the central cell.
• The fertilized ovule develops into a seed, and the ovary develops into a fruit.
• Structure of pollen- Exine(sporopollein), Intine (cellulosic + pectic) and structure of the anther- Bilobed & dithecous.

Pollen Viability

• Viability times differ based on species:
  • Wheat and Rice (30 minutes)
  • Rosaceae, Solanaceae, Leguminosae (months).

Fruit and Seed Development

• Fertilized ovules develop into seeds
• Ovaries develop into fruits
• Seed coats formed: Testa, Tegmen
• Seed types: Albuminous (e.g., wheat, maize) and non-albuminous (e.g., pea, groundnut)
• Formation of more than one embryo (polyembryony) occurs in certain plants (citrus).
• Apomixis is the formation of seeds without fertilization

Outbreeding Devices

• Prevention of self-pollination strategies:
  • Production of unisexual flowers
  • Non-synchrony of pollen and stigma receptivity
  • Position of flowers
  • Self-incompatibility.

Agents of Pollination

• Biotic (e.g., insects, birds);
  • Bee dominated
• Abiotic (e.g., wind, water)
  • Wind (Anemophily)
  • Water (Hydrophilly)
• Light pollen, exposed stamens

Other notes

• Perisperm: Persistent nucellus (e.g., black pepper, beet)
• Dormancy records: - Lupinus arcticus: 10,000 years - Phoenix dactylifera: 2,000 years
• False fruit (e.g., apple, strawberry, cashew)
• Parthenocarpic fruits (e.g., banana)

Explore the fascinating process of sexual reproduction in flowering plants, including pollen grain development, pollination methods, and fertilization. This quiz covers various types of pollination, the role of gametes, and the outcomes of double fertilization. Test your knowledge on how flowers reproduce and the agents involved in the process.