7.7 transport of water in the xylem

Question 1

what are some factors affecting rate of transpiration?

Answer 1

surface area, wind, humidity

Question 2

how does guard cells control the rate of transpiration?

Answer 2

becoming flaccid/turgid

Question 3

how does transpiration occur? (3)

Answer 3

1- water evaporates from cell walls of cells surrounding air spaces
2- as water humidity in air spaces > atmosphere
3- water vapour diffuse through stomata due to water potential gradient

Question 4

what is meant by cohesion in water?

Answer 4

water stick together by forming hydrogen bonds

Question 5

explain the cohesion-tension theory in transporting water.

Answer 5

1- cohesion in water forms long, continuous column across mesophyll cells and down the xylem
2- as water evaporates on surface of mesophyll cells, this creates a transpiration pull
3- this puts the xylem under tension and the negative pressure allows water to be pulled upwards