Pathways and Transpiration

Question 1

which pathway is used when transpiration rates are high

Answer 1

apoplastic pathway

Question 2

in the apoplastic pathway how does water move and is it passive or active

Answer 2

by diffusion, passive

water moves from cell wall to cell wall directly or through intercelular spaces

Question 3

what blocks the apoplastic pathway

Answer 3

a thick waterproof, waxy band of suberin called the casparian strip

Question 4

which pathway transports water faster

Answer 4

apoplastic pathway and slower in the sympoplastic

Question 5

describe the sympoplastic pathway

Answer 5

a small amount of water travels in the cytoplasm, plasmodesmata or vacuole
by osmosis
cell membrane to vacuole to plasmodesmata

Question 6

define transpiration

Answer 6

loss of water vapour from a plant to its environment by diffusion

Question 7

describe the process of transpiration from in the leaves

Answer 7

• a higher water potential inside the leaves and lower water potential outside the leaves results in diffusion of water vapour out of the leaves through the stomata.
• water vapour lost by transpiration lowers the water potential in air spaces surrounding the mesophyll cells
• the water in the mesophyll evaporates into the airspaces resulting in a transpiration pull
• the transporation pull results in water moving through the mesophyll cell walls apoplastically and into the vacuole sympoplastically and into the cell walls again
• this causes water to leave the xylem vessel through the pits (non-lignified holes) and again causing water to move up the xylem due to cohesive and adhesive forces of water

Question 8

state the role of stomata

Answer 8

• gaurd cells when turgid open up the stomata but when guard cells lose wate stomata closes
• open stomata = greater rate of transpiration and gas exchange
• close stomata = lower rate of transpiration and gaseous exchange