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Date May 2018 Marks available 3 Reference code 18M.3.HL.TZ1.3
Level Higher level Paper Paper 3 Time zone Time zone 1
Command term Evaluate Question number 3 Adapted from N/A

Question

Transpiration in plants can be measured using a bubble potometer or a mass potometer.

Suggest a possible research question that could be investigated using a potometer.

[2]
a.

Evaluate the limitations of using a potometer in the investigation you suggested in (a).

[3]
b.

Markscheme

a. the research question identifies the independent variables 

b. the research question identifies the dependent variable/derived value 

c. the research question identifies the organism tested 

If several variables are given, mark the first one only.

Examples:

a. Effect of changing/increasing wind/temperature/light/humidity/surface area/comparing different species

b. accept transpiration rate

c. accept common names.

a.

a. not all of the water taken up by the plant is used for transpiration 

b. some water taken up might be used for photosynthesis/ cell turgidity 

c. (bubble) potometer measures rate of water uptake (not transpiration directly)
OR
bubble in potometer may expand due to changes in temperature/pressure

d. (cut) plant/twig gets damaged/may not survive 

e. conditions in a lab are not equivalent to those in nature/ difficult to change only one abiotic factor 

f. difficult to extrapolate values from a twig to whole plant

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Additional higher level » Topic 9: Plant biology » 9.1 Transport in the xylem of plants
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Additional higher level » Topic 9: Plant biology
Additional higher level

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