4.2.5 - Gas exchange in plants

Question 1

Describe what structures you would find in a leaf from top to bottom.

Answer 1

Guard cells and stomata on surface
Upper epidermis
Pallisade mesophyll
spongy mesophyll
air spaces
lower epidermis
waxy cuticle

Question 2

What is the role of the waxy cuticle on the surface of the leaf?

Answer 2

It’s waterproof so prevents water loss by evaporation
Also allows light to enter for photosynthesis

Question 3

Describe what happens in guard cells when the conditions for photosynthesis are favourable
(stomata needs to open to allow carbon dioxide to enter)

Answer 3

1) Solutes (usually potassium ions) move into the guard cells by active transport
2) Water moves into guard cells by osmosis
3) Guard cells swell and turgor pressure increases
4) Stomata open due to uneven bending caused by the cellulose distribution

Question 4

What are lenticels and where are they found?

Answer 4

Porous tissue comprising cells and huge intercellular spaces
Found in the roots of flowering pants and the bark of woody stems.

Question 5

Differences between lenticels and stomata?

Answer 5

The opening of stomata is regulated, not for lenticels.
Stomata have guard cells, lenticels do not
Lenticels are usually found on the ste mof plants whereas stomata found on the leaves.