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Flower Dissection

In this activity, students will observe the parts of a flower and learn how each part is involved in helping a plant continue its growth for another generation.

Specifically, students will find the petals, stamens, pistils, pollen, and ovules and learn more about how a plant reproduces.

The 4 main sections of a complete flower are the sepals (generally green), petals (generally colourful), stamens (male parts), and pistils (female parts). Although these parts can be described in further detail, this activity examines them in a more general sense.  

Petals function to attract pollinators to the flower using colours, scents, heat, and different patterns visible under both ultraviolet and visible light. Sepals surround and protect the developing flowers. Once the pollinator lands on the flower, it will search for the nectar found inside of the flower. 

As they search for nectar, pollinators brush up against the stamens (male parts) and pollen sticks to their bodies. Later, as pollinators travel to other flowers, they may transfer this pollen to other flowers and some will likely land on the top of a pistil and migrate downward to fertilize the ovules (eggs) at the bottom of the pistil. These fertilized ovules will then develop into seeds.

Objectives

  • Increase their observational skills of natural objects.

  • Study different aspects of the life cycle of plants.

Materials

  • Per Group:
    2 flowers from nature or a store (Lilies work well to show all parts.)
    1 hand lens

  • Per Class:
    1 scalpel or sharp knife

Key Questions

  • How do petals help attract pollinators?
  • How many petals did you see?
  • What did you notice about the male parts?
  • What about female parts of the flower?
  • Does pollen come from the male part or the female part?
  • Could you find the eggs (ovules)/future seeds?
  • How many ovules did you see?
  • Where would the seeds grow from?
  • If fruit have seeds in them, what might be a part that develops into a fruit?

What To Do

Preparation

  1. Use a sharp knife or scalpel to divide half of the flowers you have  in half lengthwise. Ensure to cut them right through the middle region (pistil).
  2. Place flowers at separate tables. Each table should have one whole flower and two halves.
  3. Print off the above drawing, or draw out the flower parts on the black board for display.

Set up

  1. Divide students into groups of 4-5.
  2. Guide students through the parts of the flower.

Activity

  1. Have students find the petals and if the sepals, if possible. Think of how petals might help bring a pollinator to the flower.
  2. Have students tap the flower to see where pollen falls off from.
  3. Next have students examine the pistil. Have them touch the top of the pistil on the stigma. This sticky part is where pollen will land with the aid of pollinators. See if some pollen will stick to the pistil.
  4. Finally, have students look at the cut halves. Notice how they are mirror images. Have them look in the centre of the flower half to locate any unfertilized eggs.

Extensions

  • Look at parts of the flower under a microscope.
  • Compare different flowers.
  • What are some commonalities between different species?
  • Compare a flower with male and female cones of a tree.
  • Draw the flower and its parts.
  • Use this activity as an introduction to pollinators and to gain a deeper understanding of pollination.
  • Examine plants from flower stage to fruit stage to watch how a flower can change into a fruit if it is pollinated and fertilized.
  • Do a seed dissection following the flower dissection. Compare and contrast the structures that you observe.