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Date November 2019 Marks available 1 Reference code 19N.3.HL.TZ0.2
Level Higher level Paper Paper 3 Time zone TZ0 / no time zone
Command term Describe Question number 2 Adapted from N/A

Question

A student designed an experiment to study the transpiration through the leaves of a tomato plant (Solanum lycopersicum). Measurements were taken in the initial conditions with five leaves on a tomato shoot and then again after each of the five leaves was removed.

[Source: R. C. Hodson and J. Acuff . 2006. Water transport in plants: anatomy and physiology in
Tested Studies for Laboratory Teaching, Volume 27 pp 163–183]

Describe the trend in the data.

[1]
a.i.

Transpiration continued after the fifth leaf had been removed. Suggest what can be concluded.

[1]
a.ii.

State the independent variable in this investigation.

[1]
b.

Explain how the results in the graph could have been obtained.

[2]
c.

Markscheme

negative correlation between the number of leaves removed and transpiration rate Do not accept type of correlation alone, as a description is required.
OR
as more leaves are removed the transpiration rate drops ✔ OWTTE

a.i.

transpiration does not only occur in the leaves
OR
transpiration through stem/shoot ✔

a.ii.

number of leaves «removed» ✔

b.

a. using a potometer ✔ Accept transpirometer but not respirometer.

b. leafy shoot attached to a reservoir and a graduated «capillary» tube ✔

c. as transpiration increases water uptake «by roots» also increases ✔

d. distance/time for bubble «in capillary tube» to travel is used to measure transpiration rate ✔

c.

Examiners report

[N/A]
a.i.
[N/A]
a.ii.
[N/A]
b.
[N/A]
c.

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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