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Flower Anatomy: the four whorls of flowers and their functions, plus diagram and activity!

Flower anatomy is an important concept in botany! Whether you and your students are studying fruits, pollination, or plant genetics, understanding the basics of flower anatomy is important background knowledge. This post covers the basic parts of flower anatomy: the 4 “whorls” of complete flowers (sepals, petals, carpel, and stamen) as well as other basic parts supporting the flower’s structure.

In a rush? Click here to skip to printing the free flower anatomy activity!

A flower anatomy diagram of a complete flower (lily) with all four floral whorls: sepals, petals, stamens, and carpel.

Sepals

The sepals are small modified leaves located around the base of a flower. Sepals support the flower and provide protection to the other flower parts while the flower is closed before and after pollination. You can find sepals still attached to some fruits.

stem of a pink flower in macro photography
The green sepals of a sunflower. Photo by Hilary Halliwell on Pexels.com

Petals

The petals are modified leaves that help attract pollinators to the flower. Petals are often large and brightly colored, and may have patterns of colors in the ultraviolet spectrum which can be seen by insects even though it is invisible to the human eye. Petals bright colors and patterns have evolved to send a signal to pollinators: “this way to the food!”

close photography of red and pink rose
The brightly colored petals of a rose. Photo by Pixabay on Pexels.com

Stamen

The stamens are the male part of a flower that produce pollen. The job of the stamen is to ensure the pollen is gently attached to pollinators’ bodies as they visit the flower to drink nectar. Each stamen has two main parts:

  • Anther – the top portion of the stamen, which contains the pollen.
  • Filament – a short stalk supporting the anther.
purple pollen flowers
A flower with six purple and pink stamens. Photo by Anthony on Pexels.com

Carpel

The carpel is the female part of a flower that receives the pollen (also known as the pistil). The carpel awaits for pollen to be tracked onto it by a pollinator as it travels from flower to flower. The carpel has three main parts:

  • Stigma – the tip of the carpel that receives the pollen.
  • Style – a tube connecting the stigma to the ovary. Genetic materials travels from the stigma, down the style, and to the ovary.
  • Ovary – the part of the carpel that develops into a fruit after pollination. The ovary contains ovules which develop into seeds.
blooming lilium with wavy petals and pleasant scent
A flower’s carpel. The orange stigma sits atop the long green style. Photo by Skyler Ewing on Pexels.com

Pedicel

A pedicel is a short stalk holding a single flower. A stalk holding more than one flower is called a peduncle. Bothe pedicels and peduncles serve the function of supporting flowers and transporting water and nutrients to the flowers.

Receptacle

The receptacle is the thickened top portion of the pedicel that connects to the flower’s base. The receptacle supports the flower and holds the floral whorls. The receptacle becomes part of the fruit in certain fruits such as raspberries and strawberries.

Complete vs Incomplete Flowers and Perfect vs Imperfect Flowers

Flowers are classified as complete or incomplete and perfect or imperfect. Perfect flowers have both male and female parts (stamen and carpel). Imperfect flowers have either male or female parts but not both.

Any flower that has all four whorls (sepals, petals, stamens, and carpel) is called a complete flower. Complete flowers will also always be perfect flowers, but perfect flowers are not always complete. A flower that has three or fewer whorls is called an incomplete flower. A flower can be incomplete and still be perfect (for example, a flower with petals, stamens, carpel, but no sepals).

Flower Anatomy Activity

Use the link below to download and print my free flower anatomy coloring activity worksheets! Complete this flower anatomy diagram with your students by coloring in the floral parts while learning about the anatomy of flowers. Use the directions on the second page as a guide to color in the flower diagram and legend.


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