Lecture 5

Question 1

what does evaporation trigger?

Answer 1

air-water interface to retreat further into the cell and becoming more curved, increasing rate of transpiration

Question 2

does hydrostatic pressure increase or decrease as the radius of the curvature on the air-water interface increases

Answer 2

decreases

Question 3

6 steps of water movement through the leaf

Answer 3

1) stomata open

2) water vapors diffuses from internal airspace, down the concentration gradient into the air

3) net loss of water vapor causes air-water interface to recede towards microfibrils

4) H-bonding/cohesion transmits tension at surface to bulk water

5) time dependent buildup of surface tension

6) water is pulled toward the air-water interface

Question 4

when does establishment of the water potential gradient begin

Answer 4

when the air-water interface touches outer microfibrils

Question 5

what is the apoplastic pathway?

Answer 5

water moves through the intercellular space (cell walls) with no entry into the cells

Question 6

what is the symplastic pathway?

Answer 6

water moves through the cells via plasmodesmata

Question 7

what is the transcellular pathway?

Answer 7

water moves across the plasma membrane

Question 8

three things flow in pathways are determined

Answer 8

• magnitude of water potential gradient
• tissue capacitance
• resistance to water flow (Rw)