[Unit 6.4] | Gas Exchange In The Leaf Of A Plant

Question 1

Why may the use of external air involved in a plant’s gas exchange be reduced?

Answer 1

• Carbon dioxide from respiration of cells may be used for photosynthesis

• Oxygen from photosynthesis may be used in respiration
• (Though most oxygen will diffuse out of the plant)

Question 2

Why does oxygen diffuse into the cell when photosynthesis is not occurring?

Answer 2

• Oxygen is constantly used for the respiration of cells

• (Which produces Carbon Dioxide that leaves the cell)

Question 3

Describe the adaptations of the structure of a leaf in relation to gas exchange

Answer 3

• Stomata: Abundant, small pores each surrounded by a pair of guard cells that allow the pores to close
-> Plants must balance the conflicting need for preventing water loss (water leaves via evaporation) and need for gas exchange when closing the stomata

• Spongy Mesophyll: Large interconnecting air spaces that allow for ease of diffusion

• Palisade Mesophyll: Large surface area for rapid diffusion

• Upper Epidermis: