6. transport in plants Xylem

Question 1

cohesion-tension theory / how does water move up plant against force of gravity

Answer 1

1. water evaporates from leaves = tension/suction which pulls more water into leaf
2. water cohesive = whole column of water in xylem moves upwards
3. water enters stem through roots

Question 2

transpiration

Answer 2

water evaporates when stomata open (down its concentration gradient)

Question 3

transpiration rate - light

Answer 3

lighter = faster
stomata open when it gets light to allow CO2 in for photosynthesis
dark = stomata closed

Question 4

transpiration rate - temperature

Answer 4

high temperature = faster
H2O more energy - evaporate faster from cells inside leaf
increased conc gradient (in and out of leaf) making water diffuse out of leaf faster

Question 5

transpiration rate - humidity

Answer 5

lower humidity = faster

dry air = conc gradient between air and leaf increased

Question 6

transpiration rate - wind

Answer 6

more wind = faster
blows H2O from stomata
increased conc gradient

Question 7

what can be used to estimate transpiration rate

Answer 7

potometer