How Do Trees Get Their Water?

Learning Goals

By the end of the lesson, students will understand how the roots of a tree work, as well as how water travels from the roots to the leaves of a tree.

Success Criteria

• I will be able to understand how water travels through trees.
• I will be able to explain tree-related words: roots, stem, and veins.
• I will be able to make predictions and observations in a science experiment.

Materials Needed

• Leaves collected directly from a tree with stems left long- one per student or group
• Containers (preferably long and thin, such as drinking cups, so that the leaf can rest in the container without human support)- one per student or group
• Water (filled into the containers approximately ¼ of the way)
• Food colouring (a darker colour, such as red, blue, or purple- avoid yellow or green)
• Observation worksheet- one per student

Minds On (Activating Prior Knowledge)

Have a brief class discussion to gauge prior student knowledge about trees.

• “Are trees living or non-living (living)?”
• “What do many living things need to survive (oxygen and water)?”
• “Do you think trees need water to survive?”
• “How do you think trees get their water?”

Take students on a nature walk outside. Find a twig and stick it into the ground. Ask students to find their own twig and do the same. Then, ask students to try and push their twigs over. Once they are all able to push their twigs over, ask students if they know why their twigs don’t stay in the ground. Find a tree (or trees) and ask students to try to push the tree over. When they can’t, ask students:

• Why can’t you push the tree over? (The tree has roots.)
• Do you know why trees have roots? (Trees need water to survive, and the roots help the trees suck up water from the ground! The roots also hold the tree firmly in the ground so you can’t push them over easily.)

Bring students back inside. Show students pictures of different trees with their roots exposed, or show them the following YouTube video that explains how water gets carried through trees:

Activity (Teacher or Volunteer Lead)

This experiment can be done individually, in small groups, or can be performed solely by the teacher in front of students. Collect leaves ahead of time. They must be taken directly from a tree, not found on the ground, for this experiment to work (perhaps students could collect the leaves during their nature walk). Give each student or group a leaf. Ask students to recall what they just learned about trees and their roots. Ask students:

• How do you think the water reaches all the way from the roots of the tree up to the leaves?

Tell students to touch the long, stick like part of the leaf and ask if they know what this is called. Tell them it is the stem. Ask students to look at their leaves and tell you what they notice. Point out the lines running through the leaf and ask if they know what they are. Explain that they are veins. Ask if students know what the stem and veins do and explain that they carry water from the tree to the leaf.

Get a container of water (preferably tall and thin rather than short and wide) and add a few drops of food colouring to it. Ask students what they think will happen to the leaf when you place it in the water. Write down student predictions on a piece of chart paper, on the board, a google doc, etc. Place the stem of the leaf into the container of water so that the stem is submerged but the leaf is not. Let students observe for several moments (nothing will happen immediately) and explain to students that they will have to wait for several days to see what happens. Ask students:

• Why do you think this will take several days? (The water will take some time to get sucked up into the stem of the leaf and travel through the veins).

Give each student or group their own container of water and drop some food colouring into it. Have students place their leaves in the water. Put the containers in a safe place in the classroom and leave them for several days, checking them regularly and recording student observations. After several days, the stem and veins should start to turn the colour of the food colouring.

Connection + Consolidation

After the experiment, ask students:

• Why did the leaves turn the colour of the food colouring?
• Think about a tree outside. Are the veins a certain colour? Why not?

Explain to students that the veins of leaves outside are not red, blue, etc. because the water they are taking in is clean and clear.

• If the water outside is polluted, do you think the pollution would travel into the tree?
• Why would it be bad if the trees took in polluted water?

Explain to students that many animals, insects, and sometimes people eat leaves and plants. It can be very unhealthy if the water feeding the plant is polluted. Engage in a class discussion and ask students to think of ways water might get polluted.

Assessment

Have students draw/colour what their leaf looks like each day that they check it. For example, on day 1, there may be a little colour in the stem and on day 3, there may be colour throughout the whole leaf. Each day, they should be able to either verbally explain or write why their leaves are changing colour and how water is travelling through the leaf.  Check the resources sidebar for a worksheet students can use to record their observations of the leaf.

Modifications for Online Learning

If possible, use a potted plant and a picked plant to demonstrate the root minds on activity. Or, just have students think about and describe to you what would happen if they tried to push over a tree versus a twig stuck in the ground. For the leaf experiment, if possible, do the experiment in front of students. Then, return later to show them the results or take pictures of the leaf each day and send them to the class.

Another option is to perform the experiment ahead of time and have different leaves at different stages of the process to show students. For instance, for several days before this class, place a leaf into water with food colouring. After showing students how to perform the experiment, ask them their predictions about what will happen and record them.

Then, show students a leaf that has been sitting in food coloring for one day, then a leaf that has been sitting for two days, and so on. Discuss what happened to the leaf and why. Students can then try the experiment on their own (if possible).

Extension Actvities

This is an art activity that students could do after learning about trees, roots, and leaves!

Print a template of a tree (preferably one that shows roots). This template is free to download and print: http://www.supercoloring.com/coloring-pages/bare-tree-1

First, have students draw a line indicating the ground so that the roots are underneath the ground and the rest of the tree is above the ground. Then, have students colour the trunk, the background, and the underground, leaving the leaves blank. Provide students with a bundle of Q-Tips and some paint. Students dip the bundle of Q-Tips into the paint and stamp the paint onto their tree to make leaves.

Materials Needed:

• Q-Tips bundled together with an elastic band (one bundle per student)
• One blank tree template per student
• Materials to colour with (markers, pencil crayons, crayons, etc.)
• Different coloured paint
• A sample to show students (optional, examples can be found online)