Gas Exchange In Plant Leaves

Question 1

How is gas exchange with external air reduced in plants?

Answer 1

Internal photosynthesis of a plant allows gas products to be used internally without diffusion needed.

Question 2

What is happening when photosynthesis is taking place (during daylight)?

Answer 2

Some CO2 comes form respiration of cells, most is obtained from external air.
Some Oxygen is used in respiration from photosynthesis but most diffuses out of plant.

Question 3

What is happening when photosynthesis is not taking place (during darkness)?

Answer 3

Oxygen diffuses into the leaf because it is constantly being used in respiration by cells.
Carbon dioxide produced during respiration diffuses out.

Question 4

Features of efficient gas exchange of a plant leaf:

Answer 4

• No living cell is far from external air.
• Diffusion takes place in gas phase, making it more rapid.
• Air spaces have a large SA compared with vol. of living tissue.

Question 5

What are some of the leaves adaptations to ensure rapid diffusion?

Answer 5

• Many small pores, called stomata, shorten diffusion pathway.
• Air spaces throughout mesophyll allow gases to come into contact with mesophyll cells.
• Large SA of mesophyll cells for rapid diffusion.

Question 6

What are stomata?

Answer 6

Minute pores that occur mainly on the underside of leaves.

Question 7

What are the stoma (singular) operated by and how does this help with efficient gas exchange?

Answer 7

Surrounded by guard cells, which open and close the stomatal pore, to control rate of gaseous exchange and reduce water loss.