Plant gas exchange

Question 1

How are leaves adapted for gas exchange?

Answer 1

They are thin to shorten distances for diffusion and have a large surface area and are permeated by air spaces

Question 2

How are palisade mesophyll cells adapted for their function?

Answer 2

They are tall to absorb more photons of light and densely arranged in a layer, and they contain many chloroplasts

Question 3

What is the function of the waxy cuticle?

Answer 3

To reduce water loss

Question 4

Why do plants tend to close their stomata at night?

Answer 4

To reduce water loss when they are not photosynthesising

Question 5

How do guard cells open the stomata?

Answer 5

They actively transport in K+ ions and convert starch into soluble malate to lower the water potential. Water moves in by osmosis, making guard cells turgid and causing them to bend due to uneven cellulose cell wall

Question 6

How do guard cells close the stomata?

Answer 6

K+ ions diffuse out and malate is converted to insoluble starch to raise the water potential. Water moves out by osmosis and guard cells become flaccid, closing the stomata.

Question 7

How would you count the density of stomata on a leaf?

Answer 7

Apply nail varnish, peel off, put on microscope slide. Count number of stomata in three fields of view and calculate a mean.