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24 Cards in this Set

  • Front
  • Back

What is transpiration?

It is the evaporation of water vapour (diffusion) from the plants stomata into the atmosphere

What does transpiration occur as a result of?

Gas exchange

What happens during transpirtation?

*Plant opens up stomata to take in CO2 and O2 so it can photosynthesis



*But since there is lower water potential outside than in the leaves, water moves down the wp gradient and leaves our of the leaves

Four factors which effect transpiration rate:

Temperature


Humidity


Wind


Light

How does light effect the transpiration rate?

More light= Faster transpiration rate



Because the stomatal open up when there is light to take CO2 for photosynthesis but photosynthesis doesn't occur in the dark so stomatal close up

How does temperature effect the transpiration rate?

Higher temp=Faster transp rate



Greater the temperature, the more kinetic energy the molecules have so they evaporate faster. This increases the wp gradient between the inside and outside of the leaf; water diffuses out faster

How does humidity effect the rate of transpiration?

Lower humidity = Faster transp rate



If the air around the leaves is dry, there is a greater wp gradient between the leaf and the air. This increases the rate of transpiration.

How does wind effects the rate of transpiration?

Windier = Faster transpiration rate



Wind blows away water molecules surrounding the stomata. This increases the wp gradient so rate of transpiration increases.

What is the name of the plants with are adapted to reduce water loss? Live in dey conditions?

Xerophytic plants

How is maram grass adapted to reduce water loss?

*Stomata in sunken in pits; sheltered from wind- slow transpiration rate



*Hairs on surface; traps moist air around the stomata- reduces wp gradient so slows down transp rate



*Rolls up leaves when hot and windy; traps moist air so slows down transp rate. This also reduces the exposed SA from losing water and protects against wind

How Cacti adapt to reduce water loss

*Have a thick waxy layer in the epodermis; reduces water loss via evaporation because the layer is waterproof (maram grass too)



*Have spikes instead of leaves, reduces SA for water loss



*Close stomata at the hottest time of the day when transp rate is high


What is the name of the plants which are adapted to survive in water?

Hydrophilic plants

What are hydrophilic plants adapted to cope with?

Low oxygen levels

What adaptions allow hydrophilic plants to survive in water?

*Air spaces help plant float and store oxygen for respiration



*When the leaves float, they get more light so more photosynthesis



*Oxygen is able to flow to the underwater parts from the floating leaves by the air spaces in the stem



*Stomata on upper surface of floating leaves to maximise gas ex.



*Have flexible leaves and stems- so water supports the plant; no ridged stems needed. This prevents damage to the plant by water currents

Potometer experiment method:

1) Cut stem of plant at an angle (increases SA so water flows easier)



2) Cut it underwater so that the colomn of water in xylem is unbroken



3) Grease up joints to stop air bubbles entering



4) Fill potometer with H2O ensure there are no air bubbles. Introduce an air bubble into the capillary tube



5) Place the potometer underwater and top of plant into top of potometer


What does a potometer measure? Why is it only an estimate?

Water uptake, it assumes that water uptake = water transpired which is false. Some water is used by plant for photosynthesis.



Controls to keep in the potometer experiment:

Dry leaves


Keep conditions constant


Shut screw clip tight


Record position of air bubble

What does it mean for the plant in terms of transpiration, if it has more leaves?

More leaves = More stomatas


More stomatas = greater water loss



(In potometer experiment, greater movement of bubble)

What is a secondary function of water in plants?

To maintain turgor pressure in plant cells so it remains supported

What is created when water leaves the leaf?

A transpiration stream. A suction effect is created and since water is cohesive, it pulls more and more water molecules up the xylem and out of the plant

If water loss takes place and it isn't replaced what can happen to the leaf?

Cells lose turgor pressure and wilt

What's a transpiration stream?

Movement of water up xylem vessels from roots to leaves then into the surroundings

What do xylem vessel walls contain that's allows water movement between adjacent vessels?

Pits

How are xerophytic plants adapted to reduce water loss?

•Thick cuticle; reduces evaporation through leaf surface


•Folded leaf = reduces SA


•Hairs; trap water vapour