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Flower Structure and Function Flashcards

Flowers

Overview

  • Flowers are the reproductive structures of anthophytes.
  • Their color, shape, and size are determined by each species' genetic makeup.

Flower Organs

  • Flowers have several organs that provide support, protection, or are directly involved in reproduction.
  • The four main organs are:
    • Sepals
    • Petals
    • Stamens
    • Pistils

Sepals

  • Protect the flower bud.
  • Can look like small leaves or resemble the flower’s petals.

Petals

  • Colorful structures that attract pollinators.
  • Provide a landing platform for pollinators.
  • Collectively known as the corolla.

Peduncle

  • The flower stalk to which sepals and petals are attached.

Stamens

  • Male reproductive organs.
  • Consist of:
    • Filament: A stalk that supports the anther.
    • Anther: Contains cells that undergo meiosis and mitosis to produce pollen grains.

Pistil

  • Female reproductive structure.
  • Can be one or more pistils in a flower.
  • Consists of:
    • Stigma: The tip of the pistil where pollination occurs.
    • Style: Connects the stigma to the ovary.
    • Ovary: Contains one or more ovules from which the female gametophyte develops.

Flower Adaptations and Structural Differences

  • Flowers can have modifications to one or more organs.
  • Scientists categorize flowers based on these modifications.

Complete Flowers

  • Flowers that have sepals, petals, stamens, and pistils.

Incomplete Flowers

  • Flowers missing one or more of these organs.

Perfect Flowers

  • Flowers that have both stamens and pistils.

Imperfect Flowers

  • Flowers that have either functional stamens or pistils.

Monocot vs. Dicot Flowers

  • The number of flower organs distinguishes monocot and dicot flowers.
    • Monocot: Petal number is a multiple of three.
    • Dicot: Petal number is a multiple of four or five.

Pollination Mechanisms

  • Different anthophytes have adaptations related to pollination.

Self-Pollination

  • Flowers can pollinate themselves or another flower on the same plant.

Cross-Pollination

  • Flowers receive pollen grains from another plant.
  • Accomplished by pollinators.

Animal Pollination

  • Flowers are brightly colored, have strong scents, or produce nectar.
  • Insects carry pollen from one flower to another while searching for nectar.
  • White or pale flowers attract nocturnal pollinators like bats.
  • Some flowers attract fly pollinators with odors of rotting meat.
  • Bird-pollinated flowers have little to no aroma.

Wind Pollination

  • Flowers lack showy or fragrant parts.
  • Produce huge amounts of pollen grains.
  • Stigma is large to ensure pollen grain capture.

Photoperiodism

  • Plants flower at a certain time of year due to the number of hours of uninterrupted darkness.
  • This flowering response is called photoperiodism.
  • The beginning of flower development for each plant is a response to a range in the number of dark hours; this range is called the plant’s critical period.

Short Day Plants (SDP)

  • Flower when the nights are long.
  • Flower during winter and spring.

Long Day Plants (LDP)

  • Flower when the nights are short.
  • Flower during the summer.

Day Neutral Plants (DNP)

  • Largest group of flowering plants.
  • Not affected by the day length.
  • Flower at any time of the year.

Intermediate Day Plants (IDP)

  • Grow in tropical regions.
  • Flower as long as the number of hours of darkness is neither too great nor few.