A flower is the reproductive structure of an angiosperm or flowering plant. Each of the parts of a flower has a unique function that contributes to the plant’s successful reproduction. Here are the different parts of a flower, their functions, and a look at how pollination takes place.
Parts of the Flower and Their Functions
Flowers have two primary parts: the vegetative part, which includes the petals and the sepals, and the reproductive part, encompassing the stamen (male reproductive organ) and the pistil or carpal (female reproductive organ).
Vegetative Parts of a Flower (Perianth)
- Petals (Corolla): Petals are usually the most noticeable part of a flower and serve a vital function in attracting pollinators. The vibrant colors and enticing scents of petals attract pollinators such as bees, butterflies, and birds.
- Sepals (Calyx): These are small, modified leaves that enclose and protect the flower bud before it opens. They are often green, but in some flowers they are brightly colored and resemble the petals.
- Receptacle: This is the part of the flower where the flower attaches to the stalk.
- Peduncle: The peduncle is the formal name for a flower stalk.
Reproductive Parts of a Flower
The reproductive structures of flowers are separate male and female parts:
Male Parts (Stamen or Androecium)
- Anther: This part of the stamen produces and contains pollen. The anther is usually at the end of a thin tube-like structure called the filament.
- Filament: The filament is a stalk that holds up the anther, making the pollen accessible to pollinators or wind.
Female Parts (Pistil or Carpel or Gynoecium)
- Stigma: This is the part of the pistil that receives. It is often sticky or feathery for trapping and holding onto the pollen grains.
- Style: This is the long tube-like structure that connects the stigma and the ovary. Once a pollen grain lands on the stigma, it grows a pollen tube down the style to reach the ovary and accomplish fertilization.
- Ovary: This is the part of the pistil that holds the ovule(s). It is within the ovary that fertilization occurs and seeds develop.
- Ovule: The ovule is the potential seed within the ovary. Each ovule contains an egg cell. When an ovule is fertilized by a sperm cell from a pollen grain, it develops into a seed.
Worksheet: Label the Parts of a Flower
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The Function of a Flower
The primary function of a flower is reproduction, ensuring the survival of the species. Through the process of pollination and fertilization, flowers produce seeds. Each seed contains a new plant, waiting for the right conditions to grow.
Pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma. This process can occur through self-pollination or cross-pollination:
- Self-pollination: This occurs when the pollen from an anther deposits onto the stigma of the same flower or another flower on the same plant. Self-pollination is common in plants that have flowers that do not open or are not particularly showy, such as peanuts and peas.
- Cross-pollination: This occurs when pollen transfers from the anther of one flower to the stigma of another flower on a different plant of the same species. Wind, water, and animals (bees, birds, ants, bats, etc.) commonly facilitate cross-pollination. This process promotes genetic diversity among plants.
There are many different processes and agents that assist in pollination. Here are the most common ones:
- Anemophily (Wind pollination): In anemophilous plants, the flowers are usually small, inconspicuous, and produce large amounts of lightweight pollen, which is easily carried by the wind. Examples include grasses, corn, wheat, and many other grain-producing plants.
- Hydrophily (Water pollination): Hydrophilous plants are usually aquatic, with flowers that release their pollen directly onto the water’s surface. The pollen floats with water currents until it encounters a suitable stigma. Seagrasses and some species of algae exhibit this type of pollination.
- Entomophily (Insect pollination): This is the most common type of pollination process where insects, like bees, wasps, butterflies, and beetles, transfer pollen as they move from flower to flower to gather nectar. These flowers are often brightly colored and have a strong fragrance to attract insects.
- Ornithophily (Bird pollination): In ornithophilous plants, birds (e.g., hummingbirds, honeyeaters, and sunbirds) serve as the pollen vectors. These flowers are often colorful (especially red) but usually lack a strong scent, as birds have a keen vision but a poor sense of smell.
- Chiropterophily (Bat pollination): Bats pollinate certain flowers. The bats visit the flowers for nectar, pollen, or fruit. These flowers usually open at night, are large, and often have a strong, fruity or fermented odor to attract bats.
- Mammal pollination (Zoophily): Some mammals (e.g., monkeys, lemurs, possums, rodents, marsupials) help in the pollination process. The fruit or nectar of the flowers attracts them.
- Malacophily (Snail pollination): Pollen sticks to snails and deposits onto the flower’s stigma.
- Autogamy (Self-pollination): This is when the pollen from an anther falls onto the stigma of the same flower or another flower on the same plant. This process doesn’t require a pollinator.
- Geitonogamy: This is a form of self-pollination. Pollen transfers from the anther of one flower to the stigma of another flower on the same plant.
By using these different agents and methods, plants ensure that their pollen reaches the female parts of other plants, promoting genetic diversity and the continuation of their species.
- Ackerman, J. D. (2000). “Abiotic pollen and pollination: Ecological, functional, and evolutionary perspectives”. Plant Systematics and Evolution. 222 (1): 167–185. doi:10.1007/BF00984101
- De Craene, Ronse; P., Louis (2010). Floral Diagrams. Cambridge: Cambridge University Press. ISBN 978-0-511-80671-1. doi:10.1017/cbo9780511806711
- Esau, Katherine (1965). Plant Anatomy (2nd ed.). New York: John Wiley & Sons. ISBN 978-0-471-24455-4.
- Mauseth, James D. (2016). Botany: An Introduction to Plant Biology (6th ed.). Jones & Bartlett Learning. ISBN 978-1-284-07753-7.