Cells in plant roots do not photosynthesise.

Give one reason why.

• They do not have any oxygen

• They do not have any carbon dioxide

• They do not have any light for photoynthesis

• The do not have any glucose for energy

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

The diagram shows the apparatus the student used.

This is the method used.

1. Set up the apparatus as shown in the diagram above.

2. Place the lamp 10 cm from the pondweed.

3. Turn the lamp on and count the number of bubbles produced in one minute.

4. Repeat with the lamp at different distances from the pondweed.

Question

Complete the hypothesis for the student’s investigation.

‘As light intensity increases....

What was the independent variable in this investigation?

• Light Intensity

• Number of bubbles produced

• Temperature

• Time

The graph shows the effect of the concentration of carbon dioxide on the rate of photosynthesis in tomato plants at 20 °C.

Question

What is the maximum rate of photosynthesis of the tomato plants shown in the graph?

A farmer plans to grow tomatoes in a large greenhouse.

The concentration of carbon dioxide in the atmosphere is 0.04%. The farmer adds carbon dioxide to the greenhouse so that its concentration is 0.08%.

Question

(i) Why does the farmer use 0.08% carbon dioxide?

• To increase the rate of growth of the tomato plants

• To increase the rate of respiration of the tomato plants

• To increase water uptake by the tomato plants

Why does the farmer not use a concentration of carbon dioxide higher than 0.08%?

Tick 2 Correct answers

• Because it would cost more money than using 0.08%

• Because it would decrease the temperature of the greenhouse

• Because it would not increase the rate of photosynthesis of the

  tomato plants any further

• Because it would increase water loss from the tomato plants

Algae can photosynthesise.

Complete the word equation for photosynthesis.

water + ______1._________ --------> ________2._______ + oxygen

• 1 Carbon Dioxide

• 1 Glucose

• 2 Carbon Dioxide

• 2 Glucose

A student investigated the effect of temperature on the rate of photosynthesis in pondweed.

The diagram shows the way the experiment was set up.

Question

The student needed to control some variables to make the investigation fair.

State two variables the student needed to control in this investigation.

A farmer grew tomato plants in a greenhouse.

The graph shows the effect of light intensity on the rate of photosynthesis in the tomato plants growing in the greenhouse.

Question

At which light intensity was light a limiting factor for photosynthesis?

• 1

• 4

• 10

The farmer wants to increase the rate of photosynthesis in his tomato plants.

Apart from light intensity, name one factor that the farmer could change to increase the rate of photosynthesis in his tomato plants.