| Date | May 2018 | Marks available | 2 | Reference code | 18M.3.HL.TZ2.3 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Explain | Question number | 3 | Adapted from | N/A |
Question
The graph shows the effect of relative humidity on the transpiration rate in Chinese privet (Ligustrum sinense).
The rate of water uptake was measured using the potometer shown in the diagram. The diameter of the capillary tube is 1 mm.
Outline how the rate of water uptake is recorded in this potometer.
State a variable that needs to be controlled in this experiment.
Explain the effect of relative humidity on the rate of water uptake.
Markscheme
a. measure distance «of movement» of air bubble/water in capillary tube
b. multiply by cross section of capillary
c. record/divide by time elapsed
Allow any other valid method.
temperature
OR
atmospheric pressure
OR
solar radiation/light
OR
wind speed
OR
leaf area
OR
size of plant
Do not accept humidity.
a. increased «relative» humidity decreases water uptake
OR
inverse relationship
b. increased «relative» humidity lowers transpiration «rate»
c. diffusion gradient reduced «as humidity increases»
d. less loss of water through stomata
OR
stomata closed
Accept inverse for dry/low humidity.
Examiners report
Syllabus sections
- 18N.1.HL.TZ0.32: A fungicide dissolved in water was applied to the soil in which a rose plant was growing. It...
- 22M.1.HL.TZ1.32: Which graph represents the effect of humidity on the transpiration rate in plants?
- 22M.1.HL.TZ1.33: The diagrams represent cross sections of the stem and root of a plant. Which tissues...
- 17M.3.HL.TZ2.3b: Predict, with a reason, what will happen to the pressure in this tube as transpiration occurs.
- 18M.1.HL.TZ1.32: How do water molecules enter root cells? A. Transpiration B. Tension C. Capillary...
- 20N.1.HL.TZ0.32: The graph shows the percentage of stomata that are open in two different species of plants...
- 17M.1.HL.TZ1.32: Which process and cause are responsible for water uptake by the roots?
- 18M.3.HL.TZ1.3a: Suggest a possible research question that could be investigated using a potometer.
- 17M.2.HL.TZ1.4c.ii: Vascular plants can be found in a wide variety of ecosystems. Explain how a plant replaces...
- 17N.1.HL.TZ0.34: Cobalt chloride paper is blue when dry but turns pink with water. Blue cobalt chloride paper...
-
19M.3.HL.TZ1.2d.i:
Label with an R the tissue where the red dye would appear.
- 19M.2.HL.TZ1.4b: Explain how the properties of water allow it to move through xylem vessels.
- 18N.3.HL.TZ0.2c: Describe the distribution of vascular tissues in the stem of dicotyledonous plants.
-
19M.1.HL.TZ2.38:
The image is a cross section through an Ammophila leaf, which grows on coastal sand dunes.
[Source: Charles Good: The Ohio State University at Lima]
What feature suggests that Ammophila is a xerophyte?
A. The leaf surface area is increased.
B. The rolled leaf reduces the upper epidermis area.
C. The rolled leaf protects the lower epidermis from the wind.
D. The lower epidermis can transpire more easily.
- 19N.3.HL.TZ0.2b: State the independent variable in this investigation.
-
20N.3.HL.TZ0.1b:
The mean stomatal density for the lower epidermis of P. decandrum was around 600 per mm2. Predict how the stomatal density for the upper epidermis would compare.
- 17M.1.SL.TZ1.1: Which structure found in eukaryotes has a single membrane? A. Nucleus B. Lysosome C....
- 18M.3.HL.TZ2.3a: Outline how the rate of water uptake is recorded in this potometer.
- 19N.3.HL.TZ0.2a.ii: Transpiration continued after the fifth leaf had been removed. Suggest what can be concluded.
- 19N.1.HL.TZ0.32: Which process is most responsible for movement of water from roots to leaves of a plant on a...
-
19N.1.HL.TZ0.33:
In the micrograph of a plant stem, which letter indicates the xylem?
[Source: adapted from Kelvinsong/https://creativecommons.org/licenses/by/3.0/deed.en]
- 18M.3.HL.TZ2.3b: State a variable that needs to be controlled in this experiment.
-
21M.1.HL.TZ2.32:
The apparatus in the diagram was used to assess the effects of factors on transpiration rates.
[Source: Republished with permission of Springer-Verlag from Experimentelle Pflanzenphysiologie: Band 2, Peter Schopfer, 1st edition, 1st Jan 1989; permission conveyed through Copyright Clearance Center, Inc.]
Which factor would be a controlled variable in an experiment designed to assess the effects of temperature on transpiration rate?
A. The opening and closing of stomata
B. The intensity of light striking the plant
C. The height of the water in the reservoir
D. The evaporation of water from the leaves
- 19N.3.HL.TZ0.2a.i: Describe the trend in the data.
- 17M.3.HL.TZ2.3a: State the specific type of plant tissue that the plastic tube is meant to model.
- 19N.3.HL.TZ0.2c: Explain how the results in the graph could have been obtained.
-
18M.3.HL.TZ1.3b:
Evaluate the limitations of using a potometer in the investigation you suggested in (a).
-
21N.2.HL.TZ0.7b:
Distinguish between the xylem and phloem of plants.
- 19M.3.HL.TZ1.2a: State the function of the tap and reservoir.
-
19M.3.HL.TZ1.2d.ii:
Label with a C the tissue where organic compounds are transported.
-
20N.2.HL.TZ0.7b:
Describe the processes that cause water to move from the roots of plants to their leaves.
- 17M.3.HL.TZ2.3c: Outline how this control set-up could be modified to test the effect of either humidity or...
- 16N.1.HL.TZ0.32: Excessive irrigation can cause increased salinity in the soil. What effect does this have on...
- 19M.3.HL.TZ1.2c: One criticism of the experiment is that it only measured the rate of transpiration...
- 19M.2.HL.TZ1.4a: Xylem and phloem contain structures that are adapted for transport. Outline the differences...
- 19M.3.HL.TZ1.2b: Describe how the apparatus could be used to demonstrate that the transpiration rate is...
-
22M.2.HL.TZ1.6b:
Describe how changes in weather conditions affect the transport and loss of water in plants.
