| Date | November 2016 | Marks available | 2 | Reference code | 16N.3.HL.TZ0.3 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
| Command term | Describe | Question number | 3 | Adapted from | N/A |
Question
The diagram shows the development of potato plants (Solanum tuberosum) over 14 weeks. New tubers start growing from week 9. These are modified underground stems serving as a starch reserve and bearing buds from which new plants arise.
Scientists planted several potato plants in a greenhouse. The sucrose and amino acids in potato plant phloem exudates were measured during several weeks.
Describe briefly how scientists obtained leaf phloem sap from the potato plants.
Suggest reasons for different amounts of sucrose in the leaf phloem sap of the potato plants.
Markscheme
a. aphids insert stylet in «potato» plants/feed from «potato» plants
“Aphids” is essential for the mark.
b. phloem exudates/sap obtained from severed stylets
“Stylets” is essential for the mark.
a. sucrose produced by leaves during photosynthesis
b. sucrose moves/translocates from source/leaves to sink/roots/tubers
OR
sucrose carried by phloem to tuber
c. «wk 5» high sucrose with increased leaf growth/photosynthesis / OWTTE
d. «wk 5-7» more sucrose used for general plant growth / OWTTE
e. «wk 7-11» concentration sucrose increases due to greater production/photosynthesis «than usage/storage» / OWTTE
f. sucrose transformed into starch in tuber «from week 9»
g. contribution of amino acids unknown so difficult to know about different amounts of sucrose / OWTTE
Award the mark for realizing that amino acids play a role in the ratio
h. «abiotic» conditions in greenhouse may vary over time / OWTTE
Accept abiotic factors only if variation through time is explicit.
Examiners report
Syllabus sections
- 22M.1.HL.TZ2.32: The diagram shows the longitudinal section of phloem tissue at a plant source. What is...
- 18M.2.HL.TZ2.5c: Outline the process used to load organic compounds into phloem sieve tubes.
-
18M.1.HL.TZ1.33:
In a plant, what tissue(s) is/are specially adapted to transport sucrose?
- 18N.3.HL.TZ0.2c: Describe the distribution of vascular tissues in the stem of dicotyledonous plants.
-
19M.1.HL.TZ1.33:
The image shows part of a section through the stem of a non-woody plant.
[Source: © Ross Koning. Image used with the kind permission of the author. http://plantphys.info.]
Which feature distinguishes the transport of materials in the tissue labelled I from that in the tissue labelled II?
A. In II, active transport is used.
B. In II, products of photosynthesis are transported.
C. In I, movement of materials is the result of transpiration.
D. In I, there is a higher solute concentration.
- 17M.1.SL.TZ1.1: Which structure found in eukaryotes has a single membrane? A. Nucleus B. Lysosome C....
-
18M.1.HL.TZ2.29:
The micrograph shows the cross-section of the vascular tissue in a dicotyledonous root. Which letter identifies phloem sieve tubes?
[Source: Wendy Paul]
-
17N.1.HL.TZ0.33:
Which letter identifies phloem?
[Source: E R DEGGINGER/Getty Images]
-
18M.2.HL.TZ1.7c:
Explain how organic compounds are transported within plants.
-
21M.1.HL.TZ2.33:
The image shows part of a section through the stem of a non-woody plant. Where does transport of sucrose occur?
[Source: Courtesy of Kelly Cude, PhD, Professor Biological Sciences, College of the Canyons.]
- 19M.1.HL.TZ2.40: What could be used in a technique for measuring flow rates in phloem? I. Potometers II....
-
21N.2.HL.TZ0.7b:
Distinguish between the xylem and phloem of plants.
-
16N.2.HL.TZ0.7a:
Describe the transport of organic compounds in vascular plants.
- 17M.2.HL.TZ1.4c.i: Vascular plants can be found in a wide variety of ecosystems. Outline active transport in...
-
17N.2.HL.TZ0.08b:
Plants have widespread influences, from food chains to climate change.
Explain the process of water uptake and transport by plants.
- 19M.2.HL.TZ1.4a: Xylem and phloem contain structures that are adapted for transport. Outline the differences...
