What do Trees Do? Experiment A & B
Plants are fundamental to the state of a catchment. The aim of this activity is to demonstrate how plants transport water and for students to hypothesise what role this plays in a catchment.
Earth and Beyond
3.3 Students collect information which describes ways in which living things use the Earth and the sun as resources.
Life and Living
3.3 Students describe some interactions (including feeding relationships) between living things and between living and non-living parts of the environment.
Reading and following procedural text.
Writing procedural text.
Measuring liquids before and after the experiment. Measuring the mass of the celery before and after the experiment.
- fresh celery stalk with leaves
- red and blue food dye
- container to hold water
- sharp knife
- Resource Sheet 5 – Results of Experiment (PDF, 61K)*
- plastic bag (such as a large freezer bag)
- twist tie or string
This lesson has 2 parts to it.
This activity may be done as a demonstration lesson or performed in small groups. This experiment can also be used to practise altering a variable to see the effects on the transport of water in the plant.
- performing an experiment
- collecting data
Time: 30 minutes on each of 2 consecutive days
Orientating – Part A
- Cut about 2 cm off the bottom of the celery.
- Add dye to the water until it is dark red or blue.
- Place the celery in the jar and leave for 24 hours.
- After 24 hours, remove the celery and cut off the bottom 2 cm.
Ask the students to hypothesis what will happen and what the experiment is meant to demonstrate.
You could record student hypothesis in the following format.
Given ...I predict the following will occur.. .
What I did ............
What I expect to happen ..........
Take all suggestions and discuss.
Enhancing – Part A
Perform the experiment.
Return to the experiment the next day to record what happened.
Cut the celery stalk 6 cm or so from the end and record what was observed. Scrape the edge of the celery stalk and note what has happened to the dye.
Synthesising – Part A
Students record what the experiment told them about how water moves through a plant. (e.g. The experiment showed us that water can travel throughout a plant.)
For the purposes of recording and reporting the results of an experiment you may wish to create a set format (depending of the student’s level of competency) to be used. This format can be created with the students input. For an example see Resource Sheet 5 – Results of Experiment.
Orientating – Part B
- Find a tree with low branches, or a shrub.
- Place your bag over a branch containing at least six leaves.
- Close the opening by tying around the branch with twist ties or string.
- Leave for 24 hours.
- Examine the bag without removing it.
Before performing the experiment, ask students to hypothesise what will occur. You could record student hypothesise using the format shown in Part A.
What do you see in the bag? Note your observations and explain (think back to Part A).
What changes might occur in the schoolground catchment basin if many trees were cut down? Explain.
When trees are cleared and replaced with grasses or crops, would you expect more or less water to filter through to the soil/earth? Explain your answer.
When trees are cleared and replaced with grasses or crops, would you expect more or less water to leave these plants leaves and be lost to the atmosphere? Explain your answer.
Synthesising – Parts A & B
Gather the results from both experiments and ask students to summarise how water moves through plants. A labelled diagram may best show how water moves through a plant.
Ask them to suggest one of the roles plants play (other than holding the soil together and stopping erosion) in a catchment area i.e. cycling water [Growing plants use water and expel it through their leaves and consequently water is lost to the atmosphere and may become clouds then rain]. Link back to concepts such as transpiration from water cycle activities.
Individually or in groups students could draw a labelled diagram to show how trees cycle water within a catchment.
Student/s can present the experiment and results in a poster form to be displayed in the classroom.
Students can present a report (written or oral) on either experiment.
Gathering information about student learning
Sources of information could include:
- anecdotal notes on any student alternative conceptions or corrections of previous conceptions.
- anecdotal notes on student hypothesising.
- student’s labelled diagrams.
* Requires Adobe Reader
Last updated 3 September 2010