Chp 38 – Angiosperm reproduction and biotechnology

Chapter 38: Angiosperm Reproduction and Biotechnology

Overview of Angiosperms

  • Angiosperms are the most successful plant group.

  • Characterized by the life cycle stages of:

    • Flowers

    • Double Fertilization

    • Fruits

Flower Structure

  • Flowers consist of four main organs:

    • Carpel (female part):

      • Contains stigma, style, and ovary.

    • Stamen (male part):

      • Composed of filament and anther.

      • Anther contains microsporangia (pollen sacs).

    • Petals: Modified leaves surrounding reproductive organs.

    • Sepals: Protect the flower bud.

  • Mnemonic to remember floral organs: SAT-COSS (Sporophylls, Anther, Thalamus, Corolla, Ovary, Stigma, Sepals).

Types of Flowers

  • Complete Flowers:

    • Contain all floral parts.

    • Examples: Roses, lilies, apples.

  • Incomplete Flowers:

    • Lack either carpels or stamens.

    • Monoecious Plants:

      • Have both male and female flowers on the same plant (e.g., corn).

    • Dioecious Plants:

      • Separate male and female plants (e.g., Cannabis).

Pollination and Fertilization

  • Cross-Pollination Process:

    1. Pollen from stamens sticks to a bee.

    2. Bee travels to another flower to collect nectar and transfers the pollen.

  • Double Fertilization:

    • One sperm fertilizes the egg → zygote (2n).

    • Second sperm fuses with polar nuclei → endosperm (3n).

Pollination Methods

  • Types of Pollination:

    • Wind, water, animals.

    • Majority of plant species are pollinated by bees (65%).

    • Pollination by various organisms (e.g., moths, flies, bats):

      • Bees see UV radiation, prefer yellow and blue flowers.

      • Moths are attracted to fragrant, white flowers.

      • Birds prefer red, yellow, and bright flowers.

Angiosperm Life Cycle

  • Angiosperms show alternation of generations:

    • Dominant sporophyte stage (2n) and reduced gametophyte stage (n).

    • Female gametophytes occur within ovules.

    • Male gametophytes are housed in anthers.

Seed Development

  • Stages of Seed Development:

    1. Endosperm development

    2. Embryo development

    3. Seed dormancy

    4. Seed germination

    5. Seedling development

    6. Flowering

  • Seed Dormancy:

    • Mature seeds contain 5–15% water and can require environmental cues (e.g., rainfall, fire) to break dormancy.

Asexual Reproduction in Plants

  • Vegetative Reproduction: Asexual progeny arise from mature vegetative fragments.

  • Common methods include:

    • Fragmentation: Separating parts of a parent plant.

    • Apomixis: Seeds formed without fertilization.

Biotechnology in Plant Reproduction

  • Genetic Engineering and Crops:

    • Artificial selection increases desired traits in plants.

    • Genetically Modified Organisms (GMO): Organisms engineered to express specific genes from other species.

    • Examples of GMOs:

      • Bt corn, which produces a toxin against pests.

      • Biofortification to improve nutritional quality (e.g., Golden Rice).

Conclusion

  • Understanding angiosperms and their reproductive strategies is crucial in agriculture and conservation.