3.3 Transpiration Flashcards Preview

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Flashcards in 3.3 Transpiration Deck (18):
1

1. is humidity in the air more or less than the air spaces next to the stomata?

less

2

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

3. water lost from the airspaces is replaced by what?

water evaporating from cell walls of surrounding mesophyll cells

4

4. water lost by evaporation from cell walls is replaced by water from where?

the xylem by either the symplastic or apoplastic pathway

5

5. when water evaporates from mesophyll cells does it do?

lowers water potential of that cell

6

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

7. what does the water potential gradient then do?

pulls water from the xylem across the leaf mesophyll into the air

8

what is the model of water moving xylem -> leaf in a continuous stream called?

cohesion tension theory

9

why is water cohesive?

due to the hydrogen bonding between water molecules as water is a polar molecule

10

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

11

what is the purpose of stomata opening?

to allow diffusion of gases into and out the leaves
control water loss

12

what is the opening and closing of stomata controlled by?

guard cells

13

during the day what does the plant need to take in for photosynthesis?

carbon dioxide

14

at night when no oxygen is being produced the plant needs to take in oxygen for what?

cellular respiration

15

what is transpiration?

the loss/evaporation of water from the leaves and stem of a plant

16

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

17

does the transpiration pull use energy?

no

18

how is water pulled up to the leaves?

by its cohesive and adhesive nature

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