Discover how plants react to extreme weather

• A selection of potted plants, such as succulents, winter-hardy plants and indoor houseplants
• An infrared thermometer
• An ice pack
• A small lamp or torch that produces mild heat
• A stopwatch or smartphone timer
• A worksheet and pen to record measurements
• A compound microscope and glass slides (optional)

How to measure plant temperature recovery

Step 1: Record the baseline temperature

1. Choose a healthy leaf on one of your plants.
2. Measure the leaf surface temperature using the infrared thermometer.
3. Record the temperature on your worksheet.

Step 2: Test heat recovery

1. Position a lamp or torch close to the leaf for 5 minutes to simulate a heatwave.
2. Measure and record the leaf temperature immediately after heating.
3. Start your timer and measure the temperature every 1 to 2 minutes.
4. Continue until the leaf returns to its original temperature.
5. Record the total recovery time.

Step 3: Test cold recovery

1. Place an ice pack against a different leaf on the same plant for 5 minutes to simulate a cold snap.
2. Measure and record the leaf temperature immediately after cooling.
3. Start your timer and monitor the temperature every 1 to 2 minutes.
4. Continue until the leaf returns to its original temperature.
5. Compare the recovery time after cooling with the recovery time after heating.

Repeat the investigation with different plant species and compare your results.

How does plant thermoregulation work?

Plants must constantly respond to changes in their environment to survive.

One way they do this is through structures called stomata. Stomata are tiny pores on the surface of leaves that allow plants to exchange gases with the atmosphere.

When conditions are warm:

• Stomata can open to allow water vapour to escape.
• This process, known as transpiration, helps cool the leaf.
• Different plant species vary in how effectively they regulate temperature and conserve water.

Leaf structure also influences temperature regulation. Factors such as leaf thickness, water storage capacity and stomatal density affect how quickly a plant heats up, cools down and recovers from temperature stress.

Scientists study these adaptations to understand how plants respond to climate change and to identify crop varieties that can better withstand droughts, heatwaves and cold conditions.

Science fair project: Take it further

Once you have measured temperature recovery in one plant, investigate how different species respond to heat and cold.

• Compare a desert succulent with a tropical indoor plant. Which plant recovers fastest after heating? Which recovers fastest after cooling?
• Test leaves of different sizes and thicknesses. Do larger or thicker leaves respond differently to temperature changes?
• Compare plants kept in sunny and shaded locations. Does growing environment affect recovery time?
• If you have access to a microscope, make a leaf impression using clear nail polish and adhesive tape. Observe the underside of the leaf and count the number of stomata you can see. Do plants with more stomata recover differently from temperature stress?
• Create a table to record your results. Which species showed the fastest recovery times? Can you identify any patterns between leaf structure and temperature regulation?