Water Transport in Plants:
Problem and Experimental Design
You now know that water travels up through roots and stems in vascular tissue
known as xylem. The water then enters the leaf and is used in photosynthesis to
make glucose. In a tree, such as the giant redwood of California, water must
ascend over 300 feet to reach the highest leaves. This ascent requires great
forces. In this investigation, you will use young bean plants to discover details
about the forces involved. The factors involved in water transport are basically
the same in all green plants.
OBJECTIVE:
You will be expected to solve two water transport problems as stated below. You will submit
hypotheses for each problem and design and conduct your own controlled experiments. After
collecting and interpreting the data, you will decide if your hypotheses are supported or contradicted.
MATERIALS:
4-5 red kidney bean or Astro seends that have germinated
5 test tubes (150 mm x 25 mm)
beaker (600mL - 1L)
100 ml graduated cylinder
razor blade
Container for soil (for pre-lab)
scale
test tube rack
tape
sharpee
ruler
PRE-LAB ACTIVITY
1. Fill a container 1/3 full of soil. Take one bean and place it in the container, root side down.
Cover the bean with soil so that it reaches the bottom of the rim of the container. Water the
bean gently, as not to erode any soil above the bean.
2. Continue to water every other day for 2-3 weeks until all the plants have developed leaves.
DAY ONE:
The following brief pre-lab experiment will provide valuable information you will need to solve the
lab problems that follow: work as one team at your table for the pre-lab.
1. Clean out your test tubes before using them. Any contaminates may kill your plant.
2. Pour tap water into a test tube to within about 2 cm (3/4 of an inch) from the top. Use a
graduated cylinder to determine how many mL of water are in the test tube and return the water
to the test tube.
3. Pour an equal amount of water into a second test tube of the same size.
4. Record the number of mL of water placed into each tube.
5. Obtain 5 plants that are approximately the same size. You may use the ones you planted if they
are the same size,
6. Remove ONE plant from its container by gradually shaking it out over the designated
container. CAREFUL – do not rip out any of the root hairs during this process! Gently
remove all the soil from around the stem and roots. This should be done over a container; if
any soil lands on the table or floor, clean it up
immediately. If some soil remains you may rinse it in
the sink, as long as all the big chunks have been
removed first.
7. Place the bare-root bean plants carefully into one of the
tubes of water so as not to damage the roots or break
the stem. Gently push the roots to the bottom of the
tube.
8. Place this tube and the tube with water only, into a test tube rack in a warm and
lighted place in the room until the next school day. Label your test tubes and rack
with your group and period.
9. Label the remaining 4 plants with your group # and period (if they aren’t already
labeled) and give to Mrs. Cardellini.
10. Predict what will happen to the water level in each tube when you check it the
following day. This goes on the pre-lab worksheet.
11.Why was a tube set up with just water?
DAY TWO:
Pre-lab results and designing your experiments:
1. Remove the plant carefully and measure the amount of water remaining in each
tube with a graduated cylinder. Place the plant back in tube with water when
done. Any volume is fine, it’s just to keep it alive until tomorrow.
2. Create a data chart showing the original number of mL of water placed in each
tube, the number of mL today, and the difference. If there is time, you might
want to show an average and include other group’s data.
3. Explain what accounts for the loss of water in each tube.
4. How much water was actually taken up by the plant?
DESIGNING THE EXPERIMENTS (Homework):
Your obligations are as follows:
1. Create two hypotheses and design experiments to answer the two questions that
follow. Check the materials section on the previous page to see what is available
to you.
2. Perform the experiments and collect the data. (This will happen on day 4)
3. State valid interpretations and conclusions. Write a report that follows the formal
lab write-up format. (This will happen after day 5)
DESIGN EXPERIMENTS THAT WILL PROVIDE ANSWERS TO THE
FOLLOWING TWO QUESTIONS:
PROBLEM ONE:
What role does the number or size of the
leaves (leaf surface area) play in the movement
of water through a plant?
On your own paper, copy the problem and then state and label your hypothesis. Under
the methods heading, draw diagrams that would illustrate how you would set up
experiments to test your hypothesis. Remember, check the materials section on the
previous page to see what is available to you. Explain the details concerning all parts of
the experiment that aren’t clear on your diagram(s).
PROBLEM TWO:
Which force plays the most important role in
the movement of water through a plant: the
absorption of water by the roots or the
evaporation of water from the leaves?
On your own paper, copy the problem and then state and label your hypothesis. Under
the methods heading, draw diagrams that would illustrate how you would set up
experiments to test your hypothesis. Remember, check the materials section on the
previous page to see what is available to you. Explain the details concerning all parts of
the experiment that aren’t clear on your diagram(s).
DAY THREE: EXPERIMENTAL DESIGN
1. After you have designed all parts of the experiment, you will agree upon which
methods to follow as a class and carry out the experiment in small groups.
2. Remove all the plants for your group from the soil as described in step #4 from
Day 1. Place these in a beaker of water to be used the following day and label
with your group and period.
DAY FOUR: EXPERIMENTATION
1. Complete your experiment as directed.
2. Be very careful to not break the stems and leaves when placing your plants in the
test tubes.
3. Be sure to labeled your groups tubes and place them in a fully lighted area for 24
to 72 hours.
DAY FIVE: OBSERVING RESULTS
1. Gather and record all data as described in your experimental design.
2. Present your results in a clear data chart.
3. Clean all tubes, remove all tape or labels, and place all bean plants into the
container provided.
4. Turn the tubes upside down so they can dry.
DISCUSSION QUESTIONS:
1. Each of the tubes containing plants lost water. How do you know how many mL
of this water loss was due to evaporation?
2. Do the number of leaves (surface area) make a difference in water uptake in bean
plants? Explain.
3. Compare the loss of water from the tube with a whole plant (control) with the loss
of water from a tube with a plant without roots. What is the difference in values?
How many mL of water are the roots alone responsible for moving?
4. Compare the loss of water from the tube with a whole plant (control) with the loss
of water from a tube with a plant without leaves. What is the difference in values?
How many mL of water are the leaves alone responsible for moving?
5. Based upon the calculations for questions 3 and 4 above, are the roots or the
leaves responsible for moving more water?
6. Was your hypothesis for problem 2 supported, contradicted or not supported?
Write CONCLUSIONS regarding each of your hypotheses. Be sure include possible
errors.
Water Transport in Plants Pre-Lab
Name: __________________________________
Per. _______ Date: _________
Day One:
1. How much water did you put into the test tube? _______
2. Prediction (see #10 on the procedure):
3. Why set up a test tube with water and one with a plant?
4. What are the tubes called that transport water and food in a plant?
Day Two:
1. Data Chart:
2. Explain what accounts for the loss of water in each tube.
3. How much water was actually taken up by the plant each day? (show work)
4. Think about what you have learned about plants – in what areas does water move through a
plant? List them all:
Homework – Experimental Design Set-Up
Write a problem, hypothesis and create a methods diagram for both problems. You might need to
include a brief explanation in the methods for you experimental design, but it’s not required.