CIE A Level Biology

Topic Questions

A LevelBiologyCIETopic Questions14. Homeostasis14.2 Homeostasis in Plants

Syllabus Edition

First teaching 2020

Last exams 2024

|

14.2 Homeostasis in Plants

DownloadView
Easy
Medium
Hard
Easy
Medium
Hard
1a
Sme Calculator2 marks

Stomata control the movement of gases into and out of a leaf. 

State two environmental conditions that would cause stomata to close. 

How did you do?

1b
Sme Calculator1 mark

Identify the cell that controls the opening and closing of stomata.

How did you do?

1c
Sme Calculator2 marks

With the stomata closed, this offers some advantages and disadvantages to the plant. 

Explain an advantage and a disadvantage to the plant when the stomata are closed. 

How did you do?

1d
Sme Calculator3 marks

Fig. 1 shows a single stoma and surrounding cells from a xerophytic plant. The sunken stoma has been labelled for you.sunken-stoma

Fig. 1

(i)

Label two other adaptive features shown in Fig. 1 that help reduce transpiration. 

[2]

(ii)

Explain how one of these features shown in Fig. 1 helps to reduce water loss. 

[1]

How did you do?

Did this page help you?

2a
Sme Calculator3 marks

A student investigated the distribution of stomata on leaves from a species of plant. As part of their investigation they painted a thin layer of nail varnish on the lower epidermis of a leaf. They waited for the nail varnish to dry then peeled it off and placed it on a microscope slide.

The student was able to see the impressions of the stomata on the varnish using an optical microscope. She then determined the mean diameter of the stomata.

Describe how the student could use an eyepiece graticule to determine the mean diameter of stomata.

How did you do?

2b
Sme Calculator1 mark

Suggest appropriate units the student should use to measure the distribution of stomata on leaves.

How did you do?

2c
Sme Calculator2 marks

Fig. 1 shows part of the lower leaf epidermis of the plant species investigated by the student.336gdAFu_micro

Fig.1 

Calculate the number of stomata per mm2 of the leaf surface. Show your working.

How did you do?

2d
Sme Calculator3 marks

Fig. 2 shows the stomatal density of two holly leaves in two different environmental conditions.HFFZNuQn_graph

Fig. 2

(i)

Calculate the percentage difference in stomatal density between the two conditions.

[2]

(ii)

Suggest an explanation for the data shown in Fig. 2

[1]

How did you do?

Did this page help you?

3a
Sme Calculator3 marks

Guard cells surround the stomatal aperture. 

State three structural features of guard cells.

How did you do?

3b
Sme Calculator1 mark

Specific mechanisms and steps take place within the guard cells to open the stomata.

Re-order the statements below to show the steps in the correct order. 

A Thin outer cell wall of the guard cell curves causing stomata to open
B Water enters the cell through aquaporins
C Light hits the cell 
D Channel proteins open and potassium ions diffuse into the cells
E Turgor pressure is increased 
F Proton pumps actively transport hydrogen ions out of the cell

How did you do?

3c
Sme Calculator1 mark

Identify the process by which water enters the cell as described in step B in part (b).

How did you do?

3d
Sme Calculator4 marks

The hormone abscisic acid (ABA) is produced by plants to stimulate the closing of their stomata during times of water stress.

Complete the sentences below to describe the role of abscisic acid in the closure of stomata.

Choose words from the following list. You may use each word once, more than once or not at all.

proton    hydrogen   calcium    potassium   out    in  

increases    decreases   flaccid    receptors   turgid
  • ABA binds with ABA _____________ on the cell surface membrane of guard cells. 
  • This inhibits the ____________ pumps and ______________ ions are no longer actively transported out of the cell.
  • ____________ ions also move into the guard cells which stimulates the opening of further channel proteins that allow ________________ ions to leave the guard cells.
  • Water potential inside the cell ___________ and so water leaves the cell by osmosis. The guard cells become __________ and the stomata close.

How did you do?

Did this page help you?

1a
Sme Calculator2 marks

A student who wanted to investigate stomata looked at a lower leaf surface under a microscope. Their field of view is shown in Fig. 1

12

Fig. 1

The diameter of the microscope’s field of view was 1.4 mm and the lower leaf had a total surface area of 220 mm2. The area of a circle can be calculated using the following formula:

πr2

Calculate the total number of stomata on the lower surface of the student’s leaf. Give your answer to the nearest whole number.

How did you do?

1b2 marks

The student read about some research that had been carried out into the effect of atmospheric carbon dioxide on plant growth. Three different carbon dioxide levels were tested; high, medium, and low. The results relating to stomatal aperture are shown in Fig. 2. Note that the bars show standard deviation and that the term aperture refers to the opening between the guard cells. 

14-2-fig-2-2
Fig. 2

Describe what the student could conclude from Fig. 2 about the effect of atmospheric carbon dioxide on stomata.

How did you do?

1c3 marks

Suggest an explanation for the results shown in Fig. 2

How did you do?

1d3 marks

The study done by the student in part b) also looked at the effect of carbon dioxide concentration on plant biomass. Fig. 3 shows the results.

14-2-fig-2-3Fig. 3

The student concluded from Fig. 3 that the currently increasing carbon dioxide levels in the earth's atmosphere could have a positive effect on plant growth around the world.

Use Fig. 3 and your own knowledge to evaluate the student's conclusion.

How did you do?

Did this page help you?

2a3 marks

Fig. 1 shows the percentage of stomata that are open over a 96 hour period.

14-2-fig-4-1Fig. 1

(i)

Describe the opening and closing of stomata in Fig. 1.

[1]

(ii)

Other than the changing light intensity shown in Fig. 1, give two factors that could be contributing to the pattern described in part i).

[2]

How did you do?

2b2 marks

Outline why the pattern shown in Fig. 1 is advantageous to the plant.

How did you do?

2c3 marks

Research has shown that increased light intensity decreases the activity of the chemical abscisic acid (ABA) in plants.

Explain how each of the following circumstances would cause a decrease in ABA activity at increased light intensity:

(i)

Electrons from chlorophyll cause an ABA precursor molecule to be converted into a chemical called zeaxanthin.

[1]

(ii)

Glucose deactivates ABA.

[1]

(iii)

Enzymes that break down ABA are activated at high concentrations of oxygen.

[1]

How did you do?

2d6 marks

At low light intensity the level of ABA inside a plant increases.

Explain how this affects stomata.

How did you do?

Did this page help you?

1a
Sme Calculator2 marks

Fig. 1 shows a cross section of a leaf as viewed through a light microscope at x250 magnification.

81aac93d-ba35-4c7f-b936-85b4808b8009

Fig. 1

Fig. 1 indicates that the image size of a palisade mesophyll cell is 2 cm. 

Calculate the actual length of a palisade mesophyll cell.

How did you do?

1b3 marks

Identify structures P, Q, and R in Fig. 1

How did you do?

1c4 marks

(i)

Give two features of structure R that help it to carry out its function;

[2]

(ii)

Suggest how the features given in part i) help structure R to carry out its function;

[2]

How did you do?

1d1 mark

Structure R surrounds a stoma.

State the role of the stomata in plant homeostasis.

How did you do?

Did this page help you?

2a2 marks

Fig. 1 shows an electron microscope image of two guard cells.

14-2-fig-3-1Fig. 1

Give two features other than the stomatal pore that help to identify the cells in Fig. 1 as guard cells.

How did you do?

2b3 marks

If the guard cells in Fig. 1 were living, suggest the environmental conditions that might be present.

How did you do?

2c5 marks

Explain the process that would cause the size of the stomatal pore in Fig. 1 to increase.

How did you do?

Did this page help you?

3a
Sme Calculator2 marks

State the conditions in which abscisic acid (ABA) plays a role in plant physiology.

How did you do?

3b
Sme Calculator3 marks

Name and outline the roles of the two inorganic ions that play a role in the action of abscisic acid in leaf function. 

How did you do?

3c
Sme Calculator3 marks

A leaf has a surface area of 10.5 cm2 on its lower side. 

Stomata are found at a density of 112 per mm2 in the species of leaf in question.

Calculate an estimate of how many stomatal guard cells this leaf will have on its lower surface. 

How did you do?

3d
Sme Calculator2 marks

In many plant species, the guard cells on the underside of the leaf contain chloroplasts, whereas the surrounding cells of the lower epidermis do not.

This is a surprising finding given the low light intensity usually found on the underside of leaves. 

Suggest and explain a role for the chloroplasts that are found in the guard cells on the underside of leaves. 

How did you do?

Did this page help you?