6.4 gas exchange in the leaf of a plant.

Question 1

What is the difference in gas exchange between plants and animals?

Answer 1

Plants also carry out photosynthesis, where they take in carbon dioxide and produce oxygen.
- sometimes gases from one process can be used for another, reducing gas exchange with the external air

Question 2

Describe gas exchange when photosynthesis is/isn’t occurring.

Answer 2

• when photosynthesis is occurring some CO2 is obtained from respiration, but most is taken from the external air. Also, some oxygen from photosynthesis is used in respiration, but most diffuses out of the plant.
• when photosynthesis is not occurring, oxygen diffuses into the leaf and carbon dioxide diffuses out.

Question 3

How is gas exchange in plants similar to gas exchange in insects?

Answer 3

• no living cell is far from the surface, and a source of CO2 and O2.
• diffusion takes place in the gas phasewhich makes it more rapid than in water.

Question 4

how are the leaves adapted for gas exchange?

Answer 4

• many stomata so that all cells are close to one, meaning the diffusion pathway is short.
• numerous interconnecting air spaces that occur throughout the mesophyll so that gases can readily come into contact with mesophyll cells.
• large surface area of mesophyll cells for rapid diffusion.

Question 5

How do plants balance gas exchange with retaining water?

Answer 5

each stoma has a pair of guard cells around it which can open and close the pore in order to limit water loss when it would be excessive.