Transpiration And Stomata Flashcards
What are the 4 effects of transpiration rate
- Light intensity
- Temperature
- Air flow
- Humidity
How does light intensity affect
the brighter the light, the greater the transpiration rate
Stomata begin to close as it gets darker, so they need to be open so photosynthesis can happen
How does temperature affect
the warmer the faster the rate, water particles have more energy to evaporate and diffuse
How does air flow affect
the better the air flow around a leaf, the greater the transpiration, if air flow is poor, the water vapour surrounds the leaf and doesn’t move away, this means there’s a high concentration of water particles outside and inside the leaf so diffusion takes longer
How does humidity affect
The drier the air around a leaf, the faster the rate
If the air is humid there’s a lot of water, so there’s not much difference between the inside and outside
Diffusion happens fastest if there’s a good concentration gradient
How can you measure the rate of transpiration
Measure uptake of water called a potometer and record the starting position of the air bubble, start a stopwatch and record the distance moved per unit time, keep the conditions constant
How are guard cells adapted
To open and close stomata
They have a kidney shape which opens and closes the stomata
What happens when the plant has lots of water
The guard cells fill with it and it goes turgid. This makes the stomata open so gases can exchange for photosynthesis
What happens when the plant is short of water
The guard cells lose water and and become flaccid making the stomata close, this helps too much water vapour escaping
What makes the opening and closing work
Thin outer walls and thickened inner walls
They are also sensitive to light and close at night to save water without losing out on photosynthesis
What are guard cells adapted for
Gas exchange and controlling water cells
