A potometer can be used to investigate the water uptake of plants under different conditions. Figure 1.1 shows how a student investigated the effect of covering the leaves from plant shoots with grease on the water uptake of the shoots. All of the shoots were from the same plant and had 7 leaves.
Figure 1.1
When setting up the potometer in Figure 1.1, one of the precautions the students took to ensure reliable measurements of water uptake was to cut the shoots underwater.
Suggest a reason for this.Â
List three features of xylem vessels that make them specialised for the transport of water.
A potometer measures the water uptake of a plant in a given time. Water uptake does not represent the true rate of transpiration in a plant due to the other functions of water in plants.
Name three functions of water in plants (not including transpiration).
The results of the experiment are shown in the table below.
Number of leaves covered with grease on plant shoot |
Mean rate of water uptake / cm3 min-1 |
0 | 0.11 |
1 | 0.10 |
2 | 0.08 |
3 | 0.07 |
4 | 0.06 |
5 | 0.05 |
6 | 0.02 |
7 | 0.01 |
Describe the result produced when all 7 leaves have been covered in grease and suggest an explanation for this.
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