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Flower Reproduction Comprehensive Notes

Flower Reproduction

Flower

  • The flower is the reproductive organ of a plant.

  • Key parts include:

    • Stamen: The male part, collectively called the androecium.

    • Carpel: Often referred to as the pistil, the female part, collectively called the gynoecium.

Parts of a Flower and Their Functions

  • Petals: Often large and colored to attract insects.

  • Sepal: Protects the flower while it is in bud.

  • Petiole: Stalk that supports the flower, making it visible to insects and resistant to wind.

  • Nectary: Produces nectar to attract insects.

  • Stamen: The male reproductive part, composed of:

    • Anther: Contains pollen sacs where pollen grains are formed; pollen contains male sex cells.

    • Filament: Supports the anther.

  • Carpel: The female reproductive part, composed of:

    • Stigma: A sticky surface that receives pollen.

    • Style: Connects the stigma to the ovary, through which pollen tubes grow.

    • Ovary: Contains ovules, which develop into seeds after fertilization.

Flower Anatomy

  • Carpels: Produce ovules containing female gametophytes.

  • Stamens: Produce pollen grains containing male gametophytes.

  • Petals: Form the corolla.

  • Sepals: Form the calyx.

Perfect vs. Inflorescence Flowers

  • Perfect Flower: Contains both stamens and a pistil (e.g., Crateva religiosa).

  • Inflorescence: A cluster of many tiny flowers (e.g., calla lily).

    • The calla lily features tiny flowers on a central stalk surrounded by a large, petal-like bract.

References

  • Various online resources, including Oregon State University Extension, Wikipedia, IGCSE Biology, and Gardeners.com (for edible flowers).

Seed Dispersal

  • Seed dispersal is a critical process for plants to colonize new areas, reduce competition, and ensure survival.

Methods of Seed Dispersal

  • Animals:

    • Plants produce juicy fruits (e.g., cherry, hawthorn, elderberry, apple, blackberry) that animals eat, dispersing seeds through their droppings.

    • Sticky fruits (e.g., mistletoe) are spread when birds clean their beaks on tree bark.

    • Fruits with hooks and barbs (e.g., burdock) attach to animal fur.

    • Squirrels bury nuts (e.g., hazelnuts, acorns) and may not recover all of them, leading to new plant growth.

  • Wind:

    • Fruits with parachutes of hairs (e.g., dandelion, foxglove) are carried by the wind.

    • Fruits with wings (e.g., sycamore, ash) are blown over distances.

  • Water:

    • Fruits that float (e.g., water lily, pond iris, coconut) are carried by water, sometimes over long distances.

  • Explosions:

    • Plants like laburnum, broom, gorse, and peas have pods that dry and split open, throwing seeds.

Adaptations

  • Adaptation: A characteristic that helps a living thing survive in a particular environment.

  • Examples include ways plants disperse seeds, such as fruits adapted for animal consumption or seed pods that explode.

Pollination and Fertilization

Pollination

  • Transfer of pollen from the anther to the stigma.

    • Self-pollination: Pollen transfer from anther to stigma of the same flower or another flower on the same plant.

    • Cross-pollination: Pollen transfer from anther to stigma of another flower on a different plant of the same species.

Fertilization Process

  • Pollen grains land on the stigma; a pollen tube develops through the style to the ovary and ovule.

  • A male cell (haploid gamete) travels through the pollen tube to reach the ovule.

  • Fertilization: The fusion of the male nucleus with the female nucleus.

  • A zygote (diploid cell) forms when the male cell (haploid) fuses with the female egg cell (haploid).

  • The zygote undergoes cell division to form an embryo.

  • The embryo is protected inside the seed.

  • After fertilization:

    • The ovule turns into a seed; the ovule wall forms the seed coat (testa).

    • The ovary turns into a fruit (fleshy or dry).

    • Petals and sepals wither off.

Seed Dispersal: Importance

  • Colonizing New Areas: Allows plants to grow in new locations.

  • Reducing Competition: Reduces competition for light, water, and nutrients.

  • Ensuring Survival: Helps plants avoid dangers like disease or pests.

Reproduction in Plants

  • Reproduction: The process in which organisms produce young of their own kind.

Characteristics of Living Organisms

  • Reproduction, response to stimuli, nutrition, excretion, growth, respiration.

Types of Reproduction

  • Asexual Reproduction:

    • Budding.

    • Fragmentation.

    • Spore formation.

    • Vegetative propagation.

  • Sexual Reproduction:

    • Involves the fusion of male and female gametes (fertilization).

Asexual Reproduction

Processes

  • Binary Fission: (e.g., Amoeba) cell division into two identical daughter cells.

  • Budding: (e.g., Hydra) a new organism grows from an outgrowth or bud.

  • Fragmentation: (e.g., Spirogyra) an organism breaks into fragments that develop into new individuals.

  • Spore Formation: (e.g., Rhizopus) spores are released and grow into new organisms.

  • Regeneration: (e.g., Planaria) the ability to regrow lost or damaged body parts.

Sexual Reproduction

  • Involves two parents and the fusion of gametes to produce genetically different offspring.

Advantages and Disadvantages

  • Asexual Reproduction:

    • Advantages:

      • Many offspring quickly.

      • Less energy needed.

    • Disadvantages:

      • No genetic variation.

      • Overpopulation may occur.

  • Sexual Reproduction:

    • Advantages:

      • High genetic variation.

      • Diversity leads to natural selection.

    • Disadvantages:

      • More time and energy.

      • Requires two parents.

Crop Production

  • Asexual Reproduction:

    • Advantages:

      • Consistent product.

      • Faster propagation using cuttings.

    • Disadvantages:

      • More susceptible to crop diseases.

  • Sexual Reproduction:

    • Advantages:

      • Selective breeding improves crop production and quality.

    • Disadvantages:

      • Takes longer.

Plant Parts

  • Leaf, Stem, Roots, Fruit, Flower.

Flower Parts

  • Stigma, Stamen, Anther, Filament, Pistil, Style, Petals, Ovary, Sepals, Ovules, Thalamus, Pedicel.

Whorls of a Flower

  • Calyx: Composed of Sepals.

  • Corolla: Composed of Petals.

  • Androecium: Composed of Stamens (Anther and Filament).

  • Gynoecium: Composed of Pistil (Stigma, Style, Ovary, and Ovule).

Complete Flower

  • Contains Corolla, Calyx, Gynoecium, and Androecium.

Flower Types

  • Bisexual Flower: Contains both androecium and gynoecium in the same flower (e.g., Pea, China rose).

  • Unisexual Flower: Androecium and gynoecium are present in separate flowers.

    • Staminate flower (male).

    • Pistillate flower (female).

    • Examples: Maize (male and female flowers).

Pollination Types

  • Self-Pollination: Transfer of pollen from anther to stigma of the same flower.

  • Cross-Pollination: Transfer of pollen from anther to stigma of a different flower on another plant of the same species.

Agents of Pollination

  • Biotic Agents:

    • Insects.

    • Birds.

    • Artificial.

  • Abiotic Agents:

    • Wind.

    • Water.

Adaptations for Biotic Pollination

  • Insects:

    • Sticky stigma, spiky pollen, nectar, scent, bright colors, large flowers.

  • Birds:

    • Odorless flowers, brightly colored flowers, tubular flowers.

  • Artificial: Human intervention.

Adaptations for Abiotic Pollination

  • Wind:

    • Well-exposed stamen, large surface area, large quantity, dry and smooth pollen, lightweight pollen.

  • Water:

    • Pollen with specific gravity, large number of pollen.

Post-Fertilization Events

  • The ovule develops into a seed.

  • The ovary enlarges and develops into a fruit.

  • Parts of the ovule develop into the seed coat.