CP8-Water Uptake

Question 1

Objectives-investigate the effect of environment conditions on water uptake in a plant shoot

Answer 1

Objectives:

• know how to determine water update are in a leafy shoot
• be able to investigate the environmental conditions on water uptake

Question 2

Risks?

Answer 2

• capillary tubing of photometer can break easily as it is glass
• handle with care and do not apply pressure

Question 3

Method?

Answer 3

• smear petroleum jelly on joints between shoot and rubber connector to ensure an airtight seal, dry the leaves gently by blotting gently
• time the movement of air bubble along capillary tube for a set distance eg 2 cm
• record time in table
• repeat
• for temperature, conduct in water baths
• for humidity, cover shoot with clear plastic bag
• for air movement, use a fan at different distances/settings
• for light, use a lamp at different distances

Question 4

Variables?

Answer 4

IV-abiotic factor
DV-movement of air bubble so RATE of uptake of water
CV-shoot, set distance to measure rate of uptake

Question 5

Why must there be an airtight seal?

Answer 5

• otherwise water won’t be drawn up the capillary tube and no air bubble movement will be possible
• water movement in the capillary is representative of the xylem so it relies on cohesive forces between water molecules
• air bubbles prevent the cohesive forces and stop the upwards tension being transmitted through the entire water column