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Edexcel IGCSE Biology 2.57B transpiration rate factors

Edexcel IGCSE Biology 2.57B transpiration rate factors
Edexcel IGCSE Biology syllabusBiology 4BI1First assessment 2019

Practise interpreting how humidity, wind, temperature and light intensity change transpiration rate in plant data and scenarios.

How this is tested

  • compare condition sets to choose the fastest or slowest transpiration rate
  • explain graph or table trends using stomata opening, diffusion gradients and water loss
  • apply desert-plant data to judge how stomata reduce water loss in light or dry conditions

Question 2

[Maximum number: 5]

Transpiration (water loss) is affected by several environmental factors.

A student investigates the effect of light intensity on water loss from a plant shoot.
The diagram shows some of the apparatus the student uses.

Figure for Question 2 — Edexcel IGCSE Biology
Figure for Question 2 — Edexcel IGCSE Biology

The student predicts that water loss from a plant shoot will increase as light intensity increases.

Question 2(b)

(a)

Another student uses the apparatus to collect and process the data.

Table 1 shows their results.

Table 1

Table 1

[ 5 ]

Question 2(b)(i)

(i)

Explain why light intensity changes the mean volume of water lost by the shoot.

[ 2 ]

Question 2(b)(ii)

(ii)

The student repeats the experiment with a plant that is adapted to live in desert environments.

Table 2 shows the results for this desert plant.

Table 2

Table 2

The desert plant has adaptations to survive in desert environments where not much water is available.

Explain why the results for this desert plant, in table 2, are different from the results in table 1.

[ 3 ]