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Flashcards in Transpiration Extra Deck (14)
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0
Q

Which flow, apoplastic or symplastic, has more resistance?

A

Symplastic

1
Q

What is the xylem?

A

Hollow, narrow, dead vessel that is a central tube that transports water up a plant

2
Q

What is meant by the cohesion tension theory?

A

Cohesion is water molecules ‘sticking together’ due to H bonds

As water is pulled up through the xylem the xylem is put under tension

3
Q

What evidence supports cohesion tension theory?

A

‘Hug a tree’ - diameter of tree changes

When transpiration rate is high there is more tension and diameter shrinks

When there is less transpiration there is less tension so diameter increases

4
Q

What is transpiration?

A

The evaporation of water from the surface of leaves via the stomata

5
Q

How does light effect transpiration?

A

More light more transpiration

Photosynthesis only occurs in the light - Stomata are open when light for gas exchange

When stomata are open water can evaporate

6
Q

What is the effect of temperature on transpiration?

A

Increased temperature more transpiration

Kinetic energy of water molecules increases - more evaporation

Also decreases amount of water air can hold - steeper gradient

7
Q

What is the effect of wind on transpiration?

A

More wind more transpiration

Water vapour naturally accumulates around the stomata on outside of the leaf - increases water potential outside leaf

More air movement disperses this layer more quickly maintains gradient between leaf and air

8
Q

What is the effect of humidity on transpiration?

A

More humid less transpiration

More water in atmosphere so reduced gradient between leaf and atmosphere so less diffusion

9
Q

What is an xerophyte?

A

A plant that has adapted to survive in an environment with very little water

10
Q

How does a thick waxy cuticle help a plant conserve water?

A

Waxy - waterproof layer

Thick - less water can escape through

11
Q

How does rolling up leaves help a plant conserve water?

A

Helps to trap a layer of still air within the leaf

This area becomes saturated with water vapour

No gradient between inside and outside of leaf

12
Q

How do hairy leaves help a plant conserve water?

A

A thick layer of hair traps moist air next to the leaf surface

Reduces water potential gradient between inside and outside of leaf

13
Q

How do sunken stomata help a plant conserve water?

A

Stomata in pits or grooves trap a layer of water vapour outside leaf so reduce gradient

Also reduces wind movement