11. Why are epidermal cells
transparent?
to allow a lot of light to pas through
12. Vertical section through a leaf
8. Guard cell 7. stoma
1. Waxy cuticle
2. Upper epidermis
3. Palisade
mesophyll cell
4. Air space
5. Spongy mesophyll cell
6. Lower epidermis
13. QUESTION: [MAY, 2010]
Give a biological explanation for the following
statement:
Leaves are well adapted for efficient diffusion
of carbon dioxide. (4)
14. QUESTION: [MAY, 2010]
The flattened shape of leaves increases the surface
area for diffusion. 1 mark
Most plants have thin leaves – this means that the
distance for the carbon dioxide to diffuse from the
outside air to the photosynthesising cells is kept as
short as possible. 2 marks
The many air spaces inside the leaf allow carbon
dioxide to come into contact with lots of cells – this
provides lots of surface area for diffusion. 1 mark
Stomata allow carbon dioxide into the leaf. 1mark
15. Why is the upper leaf surface darker
green than the lower surface?
More chloroplasts in palisade layer than in
spongy layer.
22. Stomata are located:
mostly on the
lower leaf surface
each leaf surface
has an equal
number of stomata
23. NO stomata in
submerged leaves
Stomata only on
upper leaf surface
in floating leaves
24. Why are stomata located like this?
Lower leaf surface is
more protected from
the sun
Each leaf surface is
equally exposed to
the sun
25. Stomata are useless:
they are not in
contact with air
Stomata allow gas
exchange with the air
26. Differences between guard cells and
the surrounding epidermal cells.
Guard cells Epidermal cells
1) have chloroplasts Chloroplasts absent
2) are bean-shaped Cuboidal in shape
3) cell walls are not
evenly thick
Cell walls evenly thick