Mass Transport in Plants (AQA A Level Biology)

Exam Questions

3 hours15 questions
1a6 marks

Fill in the blanks to accurately describe the mechanism of sugar transport in plant stems. 

_________ is actively transported into the phloem by a group of specialised cells. The increased solute concentration causes the water potential to __________ in phloem and so water enters by __________. This results in a high _______ gradient causing a mass flow of water and sugar towards the _________ of the plant where the sugars are _____________ .

1b1 mark

Name the main sugar that is found in the phloem. 

1c1 mark

Figure 1 shows the cross section of a phloem in a plant.

Figure 1

HHtPNE1Y_e-q1

Identify cell type B labelled in Figure 1

1d1 mark

Using Figure 1, state one way in which the intracellular space of the sieve cells is adapted to mass transport.

Did this page help you?

2a2 marks

Holly is a common type of evergreen plant that can be found in British gardens. The leaves of holly bushes possess particularly thick waxy cuticles. A student investigated the rate of transpiration in holly leaves. He cut 10 leaves for set X and 10 leaves for set Y.  He covered the leaves in set Y in petroleum jelly.  After weighing each set of leaves he attached the leaves in each set to a separate wire.  He weighed each set of leaves at 30-minute intervals for a duration of 3 hours. His results are seen in Figure 1.

Figure 1

zIe4i-GG_e-q2

Environmental conditions can affect the rate of transpiration in plants. Name two variables which should be controlled in this investigation.

2b3 marks

In Figure 1, between 90 and 120 mins the rate of transpiration begins to slow in the leaves for both sets. Explain why this happens.    

2c3 marks

Hydrogen bonds form between polar water molecules. Describe the role that hydrogen bonding plays in the cohesion-tension theory of water transport in the xylem of plants.

2d2 marks

The results for the leaves in set X are different from the leaves in set Y.  Suggest an explanation for this.

Did this page help you?

3a1 mark

A potometer can be used to investigate the water uptake of plants under different conditions. Figure 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

6GrKuQy~_e-q3

When setting up the potometer in Figure 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. 

3b3 marks

List three features of xylem vessels that make them specialised for the transport of water.

3c3 marks

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).

3d2 marks

The results for the experiment are shown in Table 1.

Table 1

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 in Table 1 produced when all 7 leaves that have been covered in grease and suggest an explanation for this.

Did this page help you?

4a3 marks

Figure 1 shows a cross section of a stem.

Figure 1

S5yR46tf_e-q4

The structures labelled I and J in Figure 1 make up the vascular bundle. Describe the functions of the vascular bundles of plants. 

4b1 mark

Figure 2 shows how the changes in environmental temperature and light intensity throughout the day can cause the diameter of a spruce tree to fluctuate.

Figure 2

e-q42

At what time of the day is the trunk of the spruce tree most narrow?

4c3 marks

Suggest the combination of environmental factors that would result in the highest rate of transpiration in the spruce trees.

4d3 marks

Spruce trees belong to a group of plants known as conifers, which have various xerophytic adaptations. List three ways in which the leaves of xerophytic plants are adapted to live in dry environments. 

Did this page help you?

5a2 marks

A scientist is investigating substance X and its effect on the growth of new roots from acut plant stem. They used a ringing experiment to investigate the transport of substance  X through the plant stems taken from a grapefruit plant. A length of the stem was cut from each grapefruit plant and then a small block of agar placed at the top of each stem as a food source. Substance X was added to some of the agar blocks. 

Figure 1

EDIgqaC-_2

The stems were grown in the same environmental conditions for 5 weeks and then the number of roots per stem was recorded. The roots grew at the opposite end to where the agar block was located. Table 1 shows the results from the experiment.
                                                                         Table 1

Treatment Mean no. of roots per stem
1 6
2 13
3 6

 

A variety of organic substances are translocated by the phloem. Sucrose is one of the main substances. Name two others.

5b2 marks

Treatment 1 was used as a control for the experiment. Explain how the control should be treated by the scientist.

5c2 marks

Using Figure 1 and Table 1, deduce the effects of substance X on root growth.

5d3 marks

The scientist believes that substance X is transported through the plant via the phloem. Explain which results from the experiment support this belief.

Did this page help you?

1a2 marks

Privet and Holly bushes are both common types of evergreen plants that can be found in British gardens. The leaves of Holly bushes possess particularly thick waxy cuticles. A student wants to investigate the rate of transpiration in Privet and Holly leaves.

For set X he cut 10 Privet leaves and for set Y he cut 10 Holly leaves. After weighing each set of leaves he attached the leaves in each set to a separate wire. He then weighed each set of leaves at 30-minute intervals for a duration of 3 hours. His results are seen in Figure 1.

Figure 1

rSVdP3Ag_m-q1

State two variables that would affect the outcome of this experiment if not controlled.

1b2 marks

In Figure 1, the starting mean weight of the leaves in Set X was 0.1 grams. After 90 minutes the mean weight was 0.096 grams. Calculate the percentage change in weight.

1c4 marks

Use your knowledge of transpiration to explain the change in mass of the privet leaves in set X.

1d2 marks

The results shown in Figure 1 for set X are different from the results for set Y.  Suggest an explanation for this.

Did this page help you?

2a1 mark

Figure 1 shows the cross-section of a phloem in a plant.

Figure 1

UCEbbN2n_m-q2

Cell type B is characterised by a large number of mitochondria. Suggest why this is advantageous.

2b4 marks

Using Figure 1, suggest and explain two ways in which the intracellular space and walls of the sieve cells are adapted to mass transport.

2c5 marks

Describe the mechanism of sugar transport in plant stems.

2d1 mark

Most of the sugars produced by plants are used up rapidly in respiration. However, sometimes plants can overproduce sugars during photosynthesis. Describe what happens to excess sugars in plants.

Did this page help you?

3a1 mark

A potometer can be used to investigate the water uptake of plants under different conditions. Figure 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

kSewYY9n_e-q3

When setting up the potometer one of the precautions the students took to ensure reliable measurements of water uptake was to dry off the leaves. Suggest a reason for this.

3b2 marks

Give two other precautions the students should take when setting up the potometer apparatus to reliable results.

3c3 marks

A potometer measures the water uptake of a plant in a given time. Give three reasons why the measurements taken from a potometer do not represent the true rate of transpiration in a plant.

3d4 marks

The results for the experiment are shown in Table 1.

Table 1

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 and explain the results seen in
Table 1.

Did this page help you?

4a2 marks

Figure 1  below shows a transection of a stem.

Figure 1

SvJ9RZ_i_e-q4

Name the vessel J and state its function.

4b1 mark

Figure 1 shows how the changes in environmental temperature and light intensity throughout the day can cause the diameter of a spruce tree to fluctuate.

Figure 1

lXaui3Bu_e-q42

Using Figure 1, state the time range that environmental factors have the greatest impact on trunk diameter?

4c5 marks

Using the data represented in Figure 1 and your knowledge of the cohesion-tension theory, explain the changes in trunk diameter throughout the day.

4d3 marks

The scientist wanted to investigate the effect of wind on the transpiration rate of the spruce trees. He identified and labelled trees in the forest that were exposed to more windy conditions and ran the experiment again. Predict what his results will show and suggest why.

Did this page help you?

5a2 marks

A scientist is investigating two substances X and Y,  which may affect the growth of ne roots from a cut plant stem. They used a ringing experiment to investigate the transport of substances X and Y through the plant stems taken from a grapefruit plant. A length of stem from each grapefruit plant was cut and then placed a small block of agar at the top of each stem as a food source. Substance X or Y was added to some of the agar blocks.

Figure 1

h-q3

Table 1

Treatment

Mean no. of roots per stem

1 6
2 13
3 6
4 7
5 J

 

Treatment 1 was used as a control for the experiment. Explain how the result from treatment 1 is used by the scientist.

5b3 marks

Using Figure 1 and Table 1, explain the effects of substance X on root growth.

5c2 marks

Substance Y is known to be transported through the plant via the phloem. Suggest a value for J from the table in part (a) and justify your answer.

5d2 marks

During the experiment the scientist ensured that the temperature was constant for all the leaf stems. Suggest why this is important.

Did this page help you?

1a2 marks

Figure 1 shows the cross-section of a phloem in a plant.

Figure 1

rV2u2bVJ_h-q1

Name cell type B in Figure 1 and state its function.

1b5 marks

Describe how sugar is transported from the lower leaves of the plant to the growing leaf buds at the top of the plant.

1c3 marks

A scientist used radioactive carbon dioxide to investigate the direction and rate of sucrose transport in a rose plant. His results showed that during periods of plant growth sucrose was transported mostly upwards. Explain why this is happening.

1d2 marks

Most of the sugars produced by plants are used up rapidly in respiration. However, sometimes plants can overproduce sugars during photosynthesis. Excess sucrose in the sink tissues can be converted to starch. Suggest the benefits of this for maintaining the mass flow system. 

Did this page help you?

2a2 marks

A potometer can be used to investigate the water uptake of plants under different conditions. Students investigated how covering the leaves from plant shoots with grease affects the water uptake of the shoots. All of the shoots were from the same plant and had 7 leaves. The set up of their experiment is shown in Figure 1 below.

Figure 1

h-q31

When setting up the potometer shown in Figure 1 one of the precautions the students took to ensure reliable measurements of water uptake was to cut the shoots underwater. Give two other precautions the students should take when setting up the potometer apparatus to ensure reliable results.

2b3 marks

Using your knowledge of plant processes, discuss whether the measurements taken from a potometer represents the true rate of transpiration in a plant.

2c3 marks

The results for the experiment are shown in Table 1.

Table 1

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


Sketch a graph to illustrate the results in
Table 1

2d3 marks

What can you conclude about the effect of covering plant leaves with grease from the data in Table 1 and your graph? Explain how you reached your conclusions.

Did this page help you?

3a1 mark

A scientist is investigating two substances X and Y,  which may affect the growth of new roots from a cut plant stem. They used a ringing experiment to investigate the transport of substances X and Y through the plant stems taken from a grapefruit plant. A length of stem was cut from each grapefruit plant and a small block of agar was placed at the top of each stem. Substance X or Y was added to some of the agar blocks.

                                                                        Figure 1

D1~UrfO8_h-q3

The stems were grown in the same environmental conditions for 5 weeks and then the number of roots per stem was recorded. The roots grew at the opposite end to where the agar block was located. Table 1 below shows the results of the experiment. 

Table 1

Treatment Mean no. of roots per stem
1 6
2 13
3 6
4 2
5 6

 

Agar delivers substances X and Y in treatments 2-5. Suggest one other reason why agar is present in all of the treatments.

3b2 marks

What can you conclude about the action of substance Y in plants from Figure 1 and Table 1?

3c4 marks

The movement of substances through the phloem can be explained using the mass flow hypothesis. Evaluate if the data from this experiment supports the mass flow hypothesis. No statistical analysis is required.

3d3 marks

Upon further research it was discovered that substance Y could be sprayed onto the leaves of a plant and it would be absorbed into the phloem sap. Using this information, discuss the mechanism by which substance Y could act as weed control.

Did this page help you?

4a2 marks

Figure 1 shows a cross section of a stem.

Figure 1

h-q4

Label I and J from Figure 1 and state their function

I   ________________________

Function of I ________________

J  ________________________

Function of J _______________

4b6 marks

Figure 2 shows how the changes in environmental temperature and light intensity throughout the day can cause the diameter of a spruce tree to fluctuate.

Figure 2

h-q4-2

Describe and explain the trunk diameter measured at midday in Figure 2. Use your knowledge of the cohesion-tension theory.

4c1 mark

Upon further analysis of the results the scientist noticed a trend. At 12 noon the trees closer to the edge of the forest showed a greater change in trunk diameter compared to the trees in the centre of the forest. They determined the mean change in trunk diameter at 12 noon for both groups of trees.

What statistical test should the scientist use to determine if the mean changes in trunk diameter for the two groups of trees are significantly different? Give the reason for your choice.

4d3 marks

Suggest why the trees on the edge of the forest could show a greater change in trunk diameter at 12 noon. 

Did this page help you?

5a2 marks

Privet and Holly are both common types of evergreen plants that can be found in British gardens. The leaves of holly bushes possess particularly thick waxy cuticles. A  student wants to investigate the rate of transpiration in privet and holly leaves.

For set X he cut 10 privet leaves and for set Y he cut 10 holly leaves. After weighing each set of leaves he attached the leaves in each set to a separate wire. He then weighed each set of leaves at 30-minute intervals for a duration of 3 hours. His results are seen in Figure 1.

Figure 1YkctBNvq_h-q5

Environmental conditions can affect the rate of transpiration in plants. Name one of these conditions and state its effect on transpiration.

5b2 marks

In Figure 1, the starting mean mass of the leaves in Set X was 0.1 grams. After 90 minutes the mean mass was 0.096 grams. Calculate the rate of change in mass per hour.

5c4 marks

Explain the change in mass for the leaves in sets X and Y shown in Figure 1.

5d2 marks

Predict what would happen if the experiment were to carry on for 12 hours.

Did this page help you?