Transpiration Flashcards
What is transpiration?
The loss of water vapour from the upper parts of the plant
Where can evaporation occur?
It mostly leaves through the stomata because of gas exchange in photosynthesis and some from the top, but is prevented by the waxy cuticle
What happens to water in a plant?
It goes through the root into the xylem to the spongey mesophyll in cells by osmosis or the apoplast pathway.
It will evaporate through its walls.
Water vapour diffuse through the open stomata depending on the water potential difference between the leaf and outside, called the water vapour potential gradient.
The outside must be a higher water potential in the leaf than outside.
What is the function of transpiration?
Transports useful minerals up the plant
Maintains cell turgidity
Supplies water for growth, cell elongation and photosynthesis
Supplies water that keeps the plant cool in the day
How does the number and size of stomata affect the rate of transpiration?
The increased size and number increases transpiration because of the larger SA that it could occur in
How does the number of leaves affect the rate of transpiration?
The increased size and number increases transpiration because of the larger SA that it could occur in
How does the waxy cuticle affect the rate of transpiration?
The thicker the waxy cuticle the less transpiration can come out of the top
How does the light intensity affect the rate of transpiration?
The more light the more stomata open for gas exchange so more photosynthesis and transpiration
How does the temperature affect the rate of transpiration?
- Increase the evaporation rate from the cell surfaces so the cell vapour potential in the leaves rise
- Increases diffusion rate through stomata because chemicals have more energy
- Decrease relative water vapour potential of the air, so more rapid diffusion out of the leaf
How does the relative humidity affect the rate of transpiration?
Decrease water loss because of decrease in rate of water loss because of smaller water vapour potential gradient
How does the air movement affect the rate of transpiration?
Increase transpiration because water is carried away faster maintaining high gradient
How does the water availability affect the rate of transpiration?
If there is less water in the soil then there is less water that can be lost so less transpiration occurs
