Water uptake in plants

Question 1

What can change the rate of water uptake in plants?

Answer 1

environmental factors:

• light intensity
• air movement
• temperature

Question 2

What effect does light intensity have on transpiration?

Answer 2

high light intensity causes the stomata to open

this increases the rate of evaporation of water from the leaf so more water is taken up to replace this

Question 3

What effect does air movement have on transpiration?

Answer 3

Wind blows moist air away from the stomata, keeping the diffusion gradient high

so the more air movement there is, the higher the transpiration rate

Question 4

What effect does temperature have on transpiration?

Answer 4

the higher the temperature, the more energy water molecules have, so they move faster, which means a faster rate of transpiration

Question 5

How can you measure the rate of transpiration?

Answer 5

using a potometer

Question 6

How do you use a potometer?

Answer 6

• note the position of the air bubble on the ruler at the start of the investigation
• note the postition of the bubble on the ruler after a known number of minutes
• divide the distance moved by the bubble by the time taken

(rate of transpiration: distance moved/time taken)

Question 7

How do you find the volume of water taken up?

Answer 7

by finding the volume of the capillary tube between the bubbles start and finish points using the formula πr²d where r = radius and d = distance moved by bubble.

Question 8

What is a concentration gradient?

Answer 8

the difference in a gradual change in concentration between two places