Flashcards in 3.3 Transpiration Deck (18):
1. is humidity in the air more or less than the air spaces next to the stomata?
2. so what do the water molecules do (if the stomata are open) as humidity is less outside?
diffuse out airspaces into surrounding air
3. water lost from the airspaces is replaced by what?
water evaporating from cell walls of surrounding mesophyll cells
4. water lost by evaporation from cell walls is replaced by water from where?
the xylem by either the symplastic or apoplastic pathway
5. when water evaporates from mesophyll cells does it do?
lowers water potential of that cell
6. what then happens to the mesophyll cells after water has evaporated and kPa is lowered?
more water moves in to the mesophyll cell by osmosis from neighbouring cells
7. what does the water potential gradient then do?
pulls water from the xylem across the leaf mesophyll into the air
what is the model of water moving xylem -> leaf in a continuous stream called?
cohesion tension theory
why is water cohesive?
due to the hydrogen bonding between water molecules as water is a polar molecule
water is also adhesive what does this help it do?
reacts with lignin in walls of xylem to help it keep moving in a continuous stream
what is the purpose of stomata opening?
to allow diffusion of gases into and out the leaves
control water loss
what is the opening and closing of stomata controlled by?
during the day what does the plant need to take in for photosynthesis?
at night when no oxygen is being produced the plant needs to take in oxygen for what?
what is transpiration?
the loss/evaporation of water from the leaves and stem of a plant
what is a transpiration stream?
- water entering roots by osmosis
- transported up the xylem
- cohesion tension theory
- movement across leaves by osmosis
- evaporation from mesophyll cells into air spaces
- out stomata
does the transpiration pull use energy?