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CAIE A-Level Biology 14.2.1 Stomatal Responses to Environmental Change

Practise predicting stomatal change from light, CO₂, humidity, temperature, wind or water stress and evaluating the trade-off between carbon uptake and water conservation.

Syllabus
2028–2030
Course
Biology 9700
Level
A2

Exam points

  • predict stomatal opening in light or low internal carbon dioxide when water is available
  • predict closure during drought, low humidity, high temperature or strong wind
  • evaluate carbon-dioxide uptake against transpiration and maintenance of cell turgor

14.2.1—Stomata response to environmental changes question 1

[Maximum number: 2]

There are more than 600 plant species in the genus Ipomoea. Many species are grown for their attractive flowers, and some species are used as crop plants.

Scientists investigated the response of stomata to changing carbon dioxide ( CO2\mathrm{CO}_{2} ) concentrations in the beach morning glory, I. pes-caprae.

The scientists placed I. pes-caprae plants in chambers. They measured the width of open stomata (stomatal apertures) after the plants had been exposed to different CO2\mathrm{CO}_{2} concentrations for 40 minutes. Light intensity and temperature were kept constant.

The relationship between CO2\mathrm{CO}_{2} concentration and the mean width of stomatal apertures is shown in Fig. 3.2.

Fig. 3.2

Fig. 3.2

In 2016, a study measured the atmospheric CO2\mathrm{CO}_{2} concentration as 400μ mol mol−1400 \mu \mathrm{~mol} \mathrm{~mol}^{-1}.

In the future, climate change may reduce water availability and increase atmospheric CO2\mathrm{CO}_{2} concentrations in some habitats.

Suggest how the stomatal response shown in Fig. 3.2 would allow I. pes-caprae to survive the effects of climate change.

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