Topic 6

Question 1

What’s transpiration

Answer 1

Flow of water into a root, up the stem (xylem) and out of the leaves.

Question 2

What does the evaporation of water from leaves do

Answer 2

Keep leaves cool

Helps move water up the plant and dissolve mineral ions

Question 3

Factors affect transpiration

Answer 3

Bright light- more transpiration because Stomata opens wider

High temp- more transpiration because particles move faster so diffuse faster.

High wind- more transpiration because it moves water away from the stomata.

High humidity- less transpiration because water will struggle to leave the leaf because of the higher concentration of water outside.

Question 4

What does Phloem translocate

Answer 4

Sucrose is translocated (transported) in the sieve tubes

Question 5

How is phloem adapted to its function

Answer 5

Holes in the ends of cell walls so liquid can flow from one sieve cell to the next.
Pores through which sucrose solution can be pumped in or out of the companion cell.
Very small cytoplasm so there’s more room for the central channel (sieve tube)

Question 6

How is xylem adapted to its function

Answer 6

Carries water
Thick side walls + rings of lignin form rigid tubes that won’t burst or collapse + provide support for plant.
Lack of cell walls between cells means water flow isn’t slowed down.
Pores so mineral ions and water can enter and leave.
Dead cells have no cytoplasm and form empty tube for water to flow through.

Question 7

Development of xylem cells

Answer 7

During development, xylem cells die and their cell walls die creating a long tube through which water can move easily.

Question 8

How and why does a stomata open and close

Answer 8

To open: water flows into the guard cells making them rigid.
Why open: when it’s light this happens so that water can diffuse out and carbon dioxide can diffuse into the leaf so photosynthesis can happen.

To close: much less water in guard cells so they shrink in the dark.

Question 9

Labelling of a leaf + adaptations

Answer 9

Leaves are broad and flat giving them a large surface area so they can diffuse more.
Palisade cells- near top of leaf under the upper epidermis. Full of chloroplast. This and the large surface area means it can absorb a lot of light.

Air spaces provide a large area for cells to exchange gases with air.
Lower epidermis containing stomata.