Question 18N.3.SL.TZ0.1b.iii
| Date | November 2018 | Marks available | [Maximum mark: 2] | Reference code | 18N.3.SL.TZ0.1b.iii |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Discuss | Question number | b.iii | Adapted from | N/A |
A variegated Pelargonium plant was grown outdoors in a plant pot. Figure 1 shows one leaf of the Pelargonium. The plant was left in the dark for 24 hours to inhibit photosynthesis. After this time, a sketch was made of the leaf to show the colours (Figure 2), then part of the leaf was covered with black card (Figure 3). Following the exposure of the plant to sunlight for six hours, the black card was removed and the leaf tested for starch (Figure 4).
Discuss briefly whether the detection of starch in this experiment was proof that photosynthesis had occurred in the leaf.
[2]
pro (yes it could be evidence):
a. starch is a product of photosynthesis ✔
con (not necessarily evidence):
b. starch could be made elsewhere «in the plant» and transported to/stored in leaves
OR
starch could be made by another process «other than photosynthesis»
OR
starch is being detected although glucose is the direct product ✔
OWTTE
limitations of experiment:
c. starch depletion may take more than 24 hours «of dark»
OR
starch production may take more than 6 hours «of light»
OR
starch should have been measured before and after ✔
