Topic 3 - Transpiration (Paper 2)

Question 1

what is transpiration caused by?

Answer 1

the evaporation and diffusion of water from a plants surface

Question 2

why is there a transpiration stream?

Answer 2

evaporation of water from a plants surface creates a shortage of water in the leaf, so more water is drawn up from the rest of the plant, and from the roots

Question 3

what four main things affect transpiration rate?

Answer 3

light intensity, temp, wind speed and humidity

Question 4

how does light intenisty affect transpiration rate?

Answer 4

the brighter the light, the greater the transpiration rate

Question 5

how does temp affect transpiration rate?

Answer 5

the warmer it is, the greater the transpiration rate

Question 6

how does wind speed affect transpiration rate?

Answer 6

the higher the windspeed, the greater the transpiration rate

Question 7

how does humdiity affect transpiration rate?

Answer 7

the drier the air around the leaf, the greater the transpiration rate

Question 8

how would you investigate transpiration rate?

Answer 8

1. cut a shoot underwater to prevent air from entering the xylem.
2. assemble the potometer in water and insert the shoot under water, so no air can enter
3. remove the apparatus from the water but keep the end of the capillary tube in the water
4. dry the leaves, allow time for the shoot to acclimatise and shut the tap
5. remove the capillary tube so theres 1 air bubble
6. record starting position of the bubble
7. start a stopwatch and record the distance moved by the bubble per unit time