(P2)Transpiration And Translocation

Question 1

What is transpiration?

Answer 1

The loss of water by diffusion and evaporation form the leaves. The transpiration stream travels from the roots to the leaves through the xylem

Question 2

Explain the 4 stages of transpiration

Answer 2

1) water enters roots through osmosis
2) water is drawn up stem through xylem
3) water is drawn out of leaf cells and xylem
4) water vapour evaporates from leaf through the stomata

Question 3

What is the role of the stomata in transpiration?

Answer 3

When guard cells take in water by osmosis, they swell which causes the stomata to open.
When guard cells lose water, the stomata becomes flaccid and closes.

Question 4

What are the factors that affect transpiration rate?

Answer 4

Temperature, humidity, wind, light intensity

Question 5

What is translocation?

Answer 5

The transport of sucrose around a plant in the phloem

Question 6

What are the 3 stages of translocation ?

Answer 6

1) sucrose is produced in leaves from glucose in photosynthesis
2) sucrose carried around plant in phloem
3) converted into starch and stored in storage organs

Question 7

How are phloem adapted to their function?

Answer 7

Sieve tubes - very little cytoplasm, lots of space to transport sucrose
Companion cells - lots of mitochondria to provide energy for active transport of sucrose in and out of sieve tubes

Question 8

How are xylem vessels adapted to their function?

Answer 8

Dead cells - no cytoplasm, more space for water

Walls strengthened with lignin rings - stronger and doesn’t collapse