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Transpiration in action

These 2 activities allow students to observe the process of plants drawing up water and its evaporation from the leaves (evapotranspiration). Set up these activities and observe them over a period of 2 or more days.
Transpiration in celery stalks

Activity 1: Suck it up

You will need

  • 500 ml cylinder
  • food colouring
  • 400 ml of water
  • a stick of celery or a carnation with a stem
  • a notebook for your observations

What to do

  1. Put 2 cups of water into the cylinder.
  2. Cut off the end of a piece of celery or a flower stem.
  3. Place the stem in the water in the cylinder.
  4. Over the next few hours you should see the plant sucking the water up through its stem (because there are no roots).
  5. Leave your experiment somewhere safe until your next lesson.
  6. Write down, or draw, your observations. What are your conclusions?

What is happening?

The plant is drawing water up through tubes in the stem (xylem) to keep a supply of water up to the leaves. Leaves need water on small openings called stomata to keep them breathing. As long as stomata are open on the leaves, water is being evaporated through them. This process of water being drawn up by a plant and then evaporating through the leaves is called evapotranspiration.
 

Plant transpiration

Activity 2: Sweat it out

You will need

  • a small clear plastic bag
  • sticky tape
  • a live shrub (in the school yard) or a cut branch with leaves
  • a notebook for your observations.

What to do

  1. Gently put the plastic bag around a branch of a live shrub or a cut branch with leaves. Try and get lots of leaves in the bag.
  2. Seal the bag around the branch so no air can get out.
  3. Leave for 20 minutes.
  4. Write down, or draw, your observations.

What is happening?

The processes of transpiration and evaporation are very significant in the Murray–Darling Basin. Most of the time water is scarce, and a significant amount either evaporates or is transpired by plants.

During the day plants transpire or sweat. That’s the process of water evaporating through small holes in the leaves called stomata. This is a very important process because it helps to create the air we breathe.

When you put the bag around the leaves, you captured the water that was being transpired by the plant. It formed droplets, or condensed, onto the inside of the plastic bag.

Last updated: 23 June 2023