3.3 Transpiration Flashcards

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

less

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2
Q
  1. so what do the water molecules do (if the stomata are open) as humidity is less outside?
A

diffuse out airspaces into surrounding air

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

water evaporating from cell walls of surrounding mesophyll cells

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

the xylem by either the symplastic or apoplastic pathway

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

lowers water potential of that cell

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6
Q
  1. what then happens to the mesophyll cells after water has evaporated and kPa is lowered?
A

more water moves in to the mesophyll cell by osmosis from neighbouring cells

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7
Q
  1. what does the water potential gradient then do?
A

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

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8
Q

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

A

cohesion tension theory

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9
Q

why is water cohesive?

A

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

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10
Q

water is also adhesive what does this help it do?

A

reacts with lignin in walls of xylem to help it keep moving in a continuous stream

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11
Q

what is the purpose of stomata opening?

A

to allow diffusion of gases into and out the leaves

control water loss

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12
Q

what is the opening and closing of stomata controlled by?

A

guard cells

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13
Q

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

A

carbon dioxide

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14
Q

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

A

cellular respiration

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15
Q

what is transpiration?

A

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

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16
Q

what is a transpiration stream?

A
  • 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
Q

does the transpiration pull use energy?

A

no

18
Q

how is water pulled up to the leaves?

A

by its cohesive and adhesive nature