Plant Gas Exchange

Question 1

What is excretion?

Answer 1

The removal of metabolic waste from an organism.

Question 2

How do plants exchange gases?

Answer 2

By diffusion

Question 3

What does the net exchange of gases depend on?

Answer 3

Light intensity

Question 4

When does photosynthesis happen?

Answer 4

During the day only

Question 5

Why must plants respire all the time?

Answer 5

To get the energy they need to live

Question 6

In the day (high light intensity) why do plants release oxygen?

Answer 6

Because they make more oxygen by photosynthesis than they use in respiration

Question 7

Why do plants take in carbon dioxide in the daytime?

Answer 7

Because they use up more carbon dioxide than they can produce.

Question 8

What ways have leaves been adapted for efficient gas exchange?

Answer 8

Broad leaves
Thin leaves
Stomata
Guard cells
Air spaces inside the leaf

Question 9

How is broad leaves an adaptation for efficient gas exchange?

Answer 9

Larger surface area so diffusion can occur quicker

Question 10

How are thin leaves an adaptation for efficient gas exchange?

Answer 10

Gases have a short diffusion distance

Question 11

How are air spaces in the leaf an adaptation for efficient gas exchange?

Answer 11

They let gases like carbon dioxide and oxygen move easily between cells and also increases the surface area for gas exchange

Question 12

How are the stomata an adaptation for efficient gas exchange?

Answer 12

They let CO2 and O2 in an out of the cell
They close as it gets dark as photosynthesis can’t occur so they prevent water from getting out and drying out the leaf.

Question 13

How are guard cells an adaptation for efficient gas exchange?

Answer 13

They change shape to open and close the stomata

Question 14

Name an experiment that could be used for gas exchange.

Answer 14

Sodium hydrogen carbonate indicator to show changes in CO2 concentration

Question 15

Describe the set up of an experiment to test gas exchange.

Answer 15

Living leaves are placed in 3 out of 4 test tubes with a dead leaf in the last one.
One tube is placed in bright light
One is wrapped in foil (no light)
One is wrapped in tissue paper (weak light)
The dead leaf is also in bright light

Question 16

What colour would the sodium hydrogen carbonate indicator go in increasing levels of CO2?

Answer 16

yellow

Question 17

What colour would the sodium hydrogen carbonate indicator go in decreasing levels of CO2?

Answer 17

purple

Question 18

What colour is sodium hydrogen carbonate indicator?

Answer 18

orange

Question 19

What colour would the indicator go in the tube with the foil cover and why?

Answer 19

It would go yellow as more carbon dioxide is being produced because it has no light so only respiration is occurring.

Question 20

What colour would the indicator go in the tube with the tissue cover and why?

Answer 20

It would stay orange as the rates of respiration and photosynthesis are the same in the low light levels.

Question 21

What colour would the indicator go in the tube in bright light and why?

Answer 21

It would be purple as the rate of photosynthesis is much higher than the rate of respiration so more carbon dioxide is being used up/ less is being produced

Question 22

What colour would the indicator go in the test tube with the dead leaf in bright light?

Answer 22

It would have no colour change as there are no living cells.

Question 23

What is the point of having the test tube with the dead leaf in it in bright light?

Answer 23

It is there as a control factor to prove that nothing else is affecting the indicator.