Trasport In Plants - Xylem

Question 1

A student used the apparatus shown in Figure 5 and a digital balance to determine the rate of water movement in a celery stalk in grams per hour per group of xylem
vessels.

Figure 5 shows a piece of celery in a beaker of water with layer of oil on a digital balance

Q) The student measured the time taken for water movement.

Give two other measurements he made to calculate the rate of water movement

2 marks

Answer 1

1. Initial and final mass (of beaker and all contents)
2. Number of (groups of) xylem vessels

.

1) Accept change in mass/weight

1) Ignore volume

1) Reject change in mass of celery / beaker / water alone

2) Accept amount for “number”

Question 2

A student used the apparatus shown in Figure 5 and a digital balance to determine the rate of water movement in a celery stalk in grams per hour per group of xylem
vessels.

Figure 5 shows a piece of celery in a beaker of water with layer of oil on a digital balance

Q) give a reason for adding a layer of oil to the water in the beaker

1 mark

Answer 2

Prevent evaporation/ water loss
Or
(So) evaporation / water loss / transpiration only from celery

Question 3

A different student used coloured water to investigate the movement of water in leaf stalks of celery.

During the procedure she:
• cut equal lengths of stalk from each plant
• put the cut end of each stalk into coloured water
• left these stalks to take up the coloured water for 20 minutes
• used a sharp scalpel to cut slices from the stalks at 1 mm intervals until she reached a slice with no coloured water.
Figure 6 shows a slice of leaf stalk with coloured water inside groups of xylem vessels.

Explain why coloured water moved up the stalks.

• (What knowledge do you apply for this question)

3 marks

Answer 3

• Process of transpiration

1. Water evaporates/is transpired (from leaves/ stalk/celery/plant);
2. Water potential gradient/lower water potential creates tension/pulls up water
   OR
   Osmosis creates tension/pulls up water;
3. Hydrogen bonds/cohesion/adhesion maintains column;

Question 4

The student used a sharp scalpel to cut the celery. Describe how she should ensure she handled the scalpel safely during this procedure.

2 marks

Answer 4

1. Cut away from body
2. Against hard / non slip / flat surface