Limiting factors in photosynthesis

Photosynthesis is important for plant growth.

A student used pondweed to investigate photosynthesis.

Figure 3 shows the apparatus used.

This is the method used.

1. Set up the apparatus as shown in Figure 3.

2. Switch on the lamp.

3. After 1 hour, record the volume of oxygen collected in the measuring cylinder.

4. Repeat steps 1 to 3 a further four times, placing the lamp at different distances from the pondweed.

What are two control variables the student should use in the investigation?

Tick () two boxes.

Table 2 shows the results.

Describe the trend shown in Table 2.

Figure 4 shows the volume of oxygen when the lamp was 10 cm from the pondweed.

What volume of oxygen is shown in Figure 4 ?

The student repeated the investigation using a measuring cylinder with smaller

What did using smaller intervals improve?

Tick () one box.

The student did the investigation at 10 °C.

The student repeated the investigation at 20 °C.

Complete the sentence.

Choose the answer from the box.

Compared to the results at 10 °C, the volumes of oxygen collected

in one hour at 20 °C would be.

Give a reason for your answer.

Photosynthesis is important for apple trees.

Figure 5 shows a section through the leaf of an apple tree.

What is tissue A ?

Tick () one box.

The cells in tissue A contain chloroplasts.

What is the name of the green chemical in chloroplasts?

Apple scab is a disease of apple trees.

Apple scab is caused by a fungus.

Figure 6 shows a leaf from an apple tree infected with apple scab fungus.

How could the fungal infection be removed from the tree?

Tick () one box.

Infection with apple scab fungus decreases the number of chloroplasts in the leaves.

Explain why apple trees with apple scab fungus produce smaller apples than apple trees that are not infected.

Photosynthesis is important for plant growth.

A student used pondweed to investigate the rate of photosynthesis.

Figure 3 shows the apparatus used.

This is the method used.

1. Set up the apparatus as shown in Figure 3.

2. Switch on the lamp.

3. After 2 hours, record the volume of oxygen collected in the measuring cylinder.

4. Repeat steps 1 to 3 a further five times, increasing the distance between the lamp

and the pondweed each time.

5. Calculate the rate of oxygen production for each distance.

Figure 4 shows the results.

Which measuring cylinder should the student have used to give the most accurate results?

Tick () one box.

Light intensity can be calculated using the inverse square law.

The equation shows the inverse square law.

Explain how light intensity changed as the distance of the pondweed from the light source was doubled.

Include calculations in your answer.

Use data from Figure 4.

The student did the investigation at 10 °C.

The student repeated the investigation at 20 °C and again at 80 °C.

Explain how repeating the investigation at 20 °C would affect the results.

Explain how repeating the investigation at 80 °C would affect the results.

This question is about photosynthesis.

Complete the equation for photosynthesis.

Choose answers from the box.

What is the chemical formula for glucose?

Tick (✓) one box.

Give two ways plants use the glucose produced by photosynthesis.

A person has two greenhouses.

In each greenhouse, the plants:

• are all the same type

• receive the same intensity of light and the same volume of water

• grow in the same type of soil.

Figure 7 shows the greenhouses.

The person burns logs in the wood burner in greenhouse B.

Explain why the plants in greenhouse B grow faster than the plants in greenhouse A.

This question is about photosynthesis.

What is the symbol equation for photosynthesis?

Tick (✓) one box.

A student investigated the relationship between temperature and the rate

of photosynthesis.

The student measured the volume of gas produced by an aquatic plant in 1 hour.

The student collected the gas in a measuring cylinder.

Table 2 shows the results.

Describe the effect of increasing temperature on the rate of photosynthesis.

Use data from Table 2.

Explain why no gas was produced by the plant at 45 °C.

How could the student increase the accuracy of the results?

Tick (✓) one box.

A person grows tomatoes in a greenhouse.

The mean temperature of the greenhouse is 15 °C.

A heater would keep the temperature of the greenhouse at 25 °C.

Suggest two reasons against using a heater set at 25 °C in the greenhouse.

Do not refer to cost in your answer.

The person cut a stem from one of the tomato plants.

The cut stem was placed in soil to grow new roots.

Which tissue in the cut stem will differentiate into new root cells?

Tick (✓) one box.

Light intensity varies during 24 hours.

Figure 6 shows the overall exchange of carbon dioxide and oxygen for a tree at three different light intensities.

Explain the overall exchange of carbon dioxide and oxygen at the three different light intensities.

Figure 2 shows a section through a leaf.

Give one way that the palisade layer is adapted for photosynthesis.

Gases pass into and out of the leaf through small pores in the surface of the leaf.

What are the small pores labelled X called?

Tick (✓) one box.

A student viewed a section of a leaf using a microscope.

The student measured the length of one of the palisade cells.

The cell image measured 28 mm in length when viewed at a magnification of ×400

Calculate the real length of the palisade cell in millimetres (mm).

Use the equation:

Convert the real length of the cell from millimetres to micrometres (µm).

1 mm = 1000 µm

Carbon dioxide can move into and out of cells.

What is the process by which carbon dioxide can move into and out of cells?

Tick (✓) one box.

Figure 3 shows a diagram of four cells.

Each cell is surrounded by carbon dioxide molecules.

Which cell will carbon dioxide move into at the fastest rate?

Give a reason for your answer.

Tick (✓) one box.

A student investigated the effect of different colours of light on the rate of photosynthesis.

Figure 4 shows some of the apparatus the student used.

The student placed the apparatus in blue light, then in green light and then in red light.

The student measured the rate of photosynthesis in each colour of light.

What two measurements should the student make to calculate the rate of photosynthesis?

Give two variables the student should keep the same in this investigation.

Table 2 shows the results.

Complete Figure 5.

You should:

• label the y-axis

• use a suitable scale

• plot the data from Table 2 as a bar chart

• label each bar.

Look at Table 2.

What colour of light should be used to grow plants in a greenhouse?

Tick (✓) one box.

Photosynthesis is an important chemical reaction in plants.

Why is light needed for photosynthesis?

What is the equation for photosynthesis? Tick (✓) one box.

A student investigated the effect of different colours of light on the rate of photosynthesis at room temperature. The student used pondweed in water. A piece of pondweed was placed in red light, then in blue light and then in green light. Each colour of light was the same intensity. Describe how the student should make accurate measurements to obtain valid results for the rate of photosynthesis.

A scientist investigated the effect of different wavelengths of light on the rate of photosynthesis. The wavelength of light determines the colour of the light. Figure 8 shows the student’s results. Figure 9 shows the scientist’s results.

Why are the results for the two investigations presented differently?

Suggest the range in wavelength of green light. Use Figure 8 and Figure 9.

Plants absorb light for photosynthesis.

Which is the equation for photosynthesis?

Tick (✓) one box.

A student investigated the effect of light intensity on the rate of photosynthesis.

Figure 6 shows the apparatus.

This is the method used.

1. Set up the apparatus as shown in Figure 6.

2. Place the pondweed 10 cm away from the lamp.

3. Switch on the lamp.

4. Record the number of bubbles of gas produced in 5 minutes.

5. Repeat steps 2 to 4 with the pondweed at different distances from the lamp.

What was the independent variable in this investigation?

Tick (✓) one box.

The lamp gets warm when it is on. This causes the temperature of the water

to increase.

Explain how an increase in temperature would affect the results of this investigation.

Suggest one way the investigation could be improved so the temperature of the water does not increase.

Suggest two improvements to the investigation so the results would be more valid.

Do not refer to controlling the temperature of the water.

Table 2 shows the results.

Calculate the rate of photosynthesis when the pondweed was 40 cm from the lamp.

Give the rate of photosynthesis as the number of bubbles of gas produced per minute.

Give one conclusion that can be made from Table 2.

Plot the data from Table 2 on Figure 7.

Draw a line of best fit.

Predict the number of bubbles that would be produced in 5 minutes if the pondweed was 60 cm from the lamp.

Use Figure 7.

Plants absorb light for photosynthesis.

Which is the equation for photosynthesis? Tick (✓) one box.

A student investigated the effect of light intensity on the rate of photosynthesis. Figure 1 shows the apparatus.

This is the method used.

1. Set up the apparatus as shown in Figure 1.

2. Place the pondweed 10 cm away from the lamp.

3. Switch on the lamp.

4. Record the number of bubbles of gas produced in 5 minutes.

5. Repeat steps 2 to 4 with the pondweed at different distances from the lamp.

What was the independent variable in this investigation? Tick (✓) one box.

The lamp gets warm when it is on. This causes the temperature of the water

to increase.

Explain how an increase in temperature would affect the results of this investigation.

Suggest one way the investigation could be improved so the temperature of the water does not increase.

Suggest two improvements to the investigation so the results would be more valid. Do not refer to controlling the temperature of the water.

Table 1 shows the results.

Calculate the rate of photosynthesis when the pondweed was 40 cm from the lamp. Give the rate of photosynthesis as the number of bubbles of gas produced per minute.

Give one conclusion that can be made from Table 1.

Plot the data from Table 1 on Figure 2. Draw a line of best fit.

Predict the number of bubbles that would be produced in 5 minutes if the pondweed was 60 cm from the lamp. Use Figure 2.

This question is about photosynthesis and food production.

How can oxygen production be used to show the rate of photosynthesis?

Scientists investigated factors affecting the rate of photosynthesis in tomato plants. The tomato plants were growing in a commercial greenhouse in the UK during winter. Figure 5 shows the results.

The percentage of carbon dioxide in the Earth’s atmosphere is 0.04%

Name the factor that is limiting the rate of photosynthesis at point X.

Farmers growing tomatoes commercially try to control the rate of photosynthesis and

make maximum profit. A farmer can control the temperature and carbon dioxide concentration in a greenhouse.

What is the minimum light intensity a farmer should use to get the maximum rate of photosynthesis shown in Figure 5 ?

The light intensity you gave in Question 05.3 may not give the farmer maximum profit. Explain why.

Explain the results when the light intensity was 0 lux. Use Figure 5.

A student investigated the effect of light intensity on the rate of photosynthesis.

Figure 1 shows some of the apparatus used.

Name the gas produced by the pondweed in the light.

Describe one way the student could change the intensity of light reaching the pondweed.

Describe how the student could use the apparatus in Figure 1 to measure the rate of photosynthesis.

Figure 2 shows the student’s results.

What was the maximum rate of photosynthesis?

At which light intensity was light a limiting factor?

Tick (✓) one box.

Light intensity can affect the rate of photosynthesis.

Give one other factor that can affect the rate of photosynthesis.

This question is about photosynthesis.

What are the two products of photosynthesis?

Tick two boxes.

A student investigated the effect of light intensity on the rate of photosynthesis.

Figure 4 shows the apparatus.

This is the method used.

1. Place the pondweed at 5 cm from the light source.

2. Measure the rate of photosynthesis by counting the number of bubbles produced in 30 seconds.

3. Repeat the investigation with the pondweed at different distances from the light source.

How could the student measure the rate of photosynthesis more accurately?

Tick two boxes.

The LED light source does not get hot.

Why is this important?

Table 1 shows the student’s results.

Calculate the number of bubbles produced in 2 minutes when the light source was 10 cm from the pondweed.

Plot the data from Table 1 on Figure 5

Draw a line of best fit.

Give one conclusion that can be made from these results.

This question is about photosynthesis.

What is the correct balanced equation for photosynthesis? Tick one box.

What type of reaction is photosynthesis? Tick one box.

A student investigated the effect of light intensity on the rate of photosynthesis. Figure 5 shows the apparatus used.

Sodium hydrogencarbonate solution releases carbon dioxide gas for the pondweed. This is the method used.

1. Place the pondweed at 5 cm from the light source.

2. Measure the rate of photosynthesis by counting the number of bubbles produced in 1 minute.

3. Repeat with the pondweed at 10 cm and at 20 cm from the light source.

Counting the number of bubbles produced in 1 minute is not an accurate way to measure the rate of photosynthesis. Suggest two ways the method could be improved to measure the rate of photosynthesis more accurately.

The LED light source does not get hot. Explain why it is important that the pondweed remains at a constant temperature.

Light intensity can be calculated using the inverse square law:

Where I is light intensity and d is the distance of the pondweed from the light source. The student placed the pondweed at 5, 10 and 20 cm from the light source. Explain how light intensity changes as the distance of the pondweed from the light source is doubled. You must include calculations in your answer.

The student’s results are shown in Table 1

Predict how many bubbles of gas would be produced in 1 minute if the pondweed was placed 40 cm from the light source. Give a reason for your prediction.

Describe how the student could change the method to investigate the effect of carbon dioxide concentration on the rate of photosynthesis. You should include:

• how to change the independent variable

• two control variables.

Use Figure 5 on page 9 to help you answer this question.