New
New
Year 11
OCR
Higher

The effect of light on water uptake by a plant: practical

I can use a simple potometer to investigate the effect of light on water uptake by a plant.

New
New
Year 11
OCR
Higher

The effect of light on water uptake by a plant: practical

I can use a simple potometer to investigate the effect of light on water uptake by a plant.

Lesson details

Key learning points

  1. Practical demonstration of the use of a simple potometer to measure water uptake by a leafy shoot.
  2. Use of a light source to vary light intensity.
  3. Use of appropriate apparatus to control temperature (e.g. a water tank as a heat shield between light and plant).
  4. Use of a simple potometer to measure water uptake by a plant at a range of light intensities.
  5. Rate of water uptake = change in volume of water ÷ time taken for volume to change

Common misconception

Being able to explain the set up of a potometer is difficult because it has so many stages that are tricky.

The stages of setting up a potometer are broken down into four parts, checked for understanding, reinforced with a lab demonstration video and concluded with a cartoon task.

Keywords

  • Transpiration - the loss of water from a plant’s leaves

  • Potometer - a piece of equipment used to measure the rate of water uptake by a plant

  • Control - a variable which is kept constant between all experiments

  • Light intensity - the amount of light reaching a given area in a given time

  • Rate - a measure of how much change occurs per unit of time

Demonstrate the set up of a potometer, and perhaps if you have time, allow students to simulate parts or all of the set up process. Running the practical is optional, as it takes a while and can yield poor quality data.
Teacher tip

Equipment

Optional: potometer, leafy shoot, clamps, clamp stand, large beaker, tripod, gauze, lamp, metre rule, timer.

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
What do plants need to perform photosynthesis?
carbon dioxide, oxygen, and water
oxygen, light, and glucose
Correct answer: water, light, and carbon dioxide
water, oxygen, and sunlight
Q2.
Which part of the plant is primarily responsible for water absorption?
flowers
leaves
Correct answer: roots
stems
Q3.
What is the function of stomata in leaves?
Correct answer: gas exchange and water loss
nutrient absorption
photosynthesis
water uptake
Q4.
What is transpiration?
the absorption of nutrients by roots
the exchange of gases in leaves
the process of photosynthesis
Correct answer: the process of water loss from the leaves
Q5.
What is the transportation stream?
the flow of water in a river
the evaporation of water from the leaf of a plant
Correct answer: the movement of water and dissolved minerals through a plant
Q6.
How do you calculate the rate of a process?
Correct answer: change ÷ time taken
change × time taken
time taken ÷ change

6 Questions

Q1.
What does a potometer measure?
the rate of gas exchange
the rate of photosynthesis
the rate of transpiration
Correct answer: the rate of water uptake by a plant
Q2.
How does light intensity affect the rate of water uptake in plants?
Higher light intensity decreases the rate of water uptake.
Correct answer: Higher light intensity increases the rate of water uptake.
Light intensity has no effect on water uptake.
Lower light intensity increases the rate of water uptake.
Q3.
What is the formula to calculate the rate of water uptake?
Correct answer: change in volume of water ÷ time taken
change in volume of water × time taken
volume taken ÷ time change
time taken ÷ change in volume of water
Q4.
Why is a beaker of water used in this experiment?
An image in a quiz
Correct answer: to control temperature
to increase light intensity
to measure light intensity
to protect the plant from water loss
Q5.
What are the roles of stomata in leaves?
Correct answer: gas exchange
nutrient absorption
photosynthesis
Correct answer: to control water loss
Q6.
During a potometer experiment lasting 20 minutes, the start reading was 0.5 cm³ and the end reading was 3.2 cm³. What is the rate of water uptake?
Correct answer: 0.135 cm³/min
0.105 cm³/min
0.145 cm³/min
0.120 cm³/min

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