Flower Structures

Flower Structures

  • Introduction to Plant Science

    • Key focus on types of flower structures and their characteristics.

Flowers and Inflorescences

  • Function of Flowers

    • Main purpose is reproduction.

Parts of a Typical Flower

  • Key Components

    • A complete flower generally consists of four main parts:

    • Petals

    • Sepals

    • Stamens (male part)

    • Pistil (female part)

    • Figure 6.35 shows a complete flower structure (apricot) with a superior ovary and a simple pistil.

Flower Classification

  • Completeness

    • Complete Flower: Has all four main parts (petals, sepals, stamens, pistil).

    • Incomplete Flower: Missing any one of the four primary parts.

  • Perfection

    • Perfect Flower: Contains both reproductive structures (stamens and pistil).

    • Pistil (female): Gynoecium

    • Stamens (male): Androecium

    • Imperfect Flower: Missing one of the reproductive structures.

    • Staminate Flower: Contains only stamens.

    • Pistillate Flower: Contains only pistils.

Flower Classification - Monoecious and Dioecious Plants

  • Monoecious Plants

    • Produce separate male (staminate) and female (pistillate) flowers on the same plant.

    • Examples: Corn, pumpkin.

  • Dioecious Plants

    • Staminate and pistillate flowers are borne on separate plants. Each plant is either male or female.

    • Examples: Ginkgo, asparagus, date palm.

Floral Arrangement on the Stem

  • Flowers can be:

    • Solitary: Only one flower on a stem.

    • Examples: Standard rose, standard carnation.

    • Inflorescences: Groups of flowers arranged on a stem.

    • Classified based on distribution and arrangement of flowers on the peduncle.

Types of Inflorescences

  • Basic Definitions:

    • Peduncle: Main stem of inflorescence or solitary flower.

    • Pedicle: Stem supporting an individual flower in an inflorescence.

Types of Inflorescences Explained:

  1. Spike

    • Unbranched and elongated; flowers are sessile (attached directly to peduncle).

    • Examples: Wheat, barley, rye, gladiolus.

  2. Raceme

    • Indeterminate, simple inflorescence where each flower has a pedicel.

    • Examples: Mustards, cole crops.

  3. Panicle

    • Indeterminate inflorescence with branching, individual branches can be raceme or corymb-like.

    • Examples: Grasses, hydrangea.

  4. Corymb

    • Indeterminate with a flat top, outer flowers open first.

    • Example: Yarrow.

  5. Umbel

    • Indeterminate; pedicles and peduncles arise from a common point, resembling an umbrella.

    • Some are compound (multiple layers).

  6. Cyme

    • Determinate inflorescence, flat-topped, outer flowers open last.

    • Examples: Strawberry, chickweed.

  7. Composite Head

    • Dense cluster of flowers with two types:

      • Ray Flowers: Outer flowers modified with extended corolla.

      • Disk Flowers: Tubular flowers at the center.

    • Examples: Sunflower, daisy.

  8. Spadix

    • Thick, fleshy flower spike surrounded by a leaf or bract called a spathe.

    • Examples: Calla lily, peace lily.

Inflorescences to Identify

  • Solitary

  • Spike

  • Raceme

  • Panicle

  • Cyme

  • Indeterminate Umbel

  • Indeterminate Corymb

  • Catkin (Ament)

  • Spadix (Surrounded by a Spathe)

  • Composite Head (Determinate)