Transpiration and stomata Flashcards
what are the 4 main things the transpiration rate is affected by
light intensity, temperature, air flow and humidity
how does light intensity affect transpiration rate and the stomata
the brighter the light, the greater the transpiration rate.
stomata begins to close as it gets darker. Photosynthesis cant happen in the dark, so they don’t need to be open to let CO2 in.
how does temperature affect transpiration rate and the stomata
the warmer it is, the faster transpiration happens.
when it is warm the water particles have more energy to evaporate and diffuse out of the stomata
how does air flow affect transpiration rate
the better the air flow around a leaf, the greater the transpiration rate. If air flow around a leaf is poor, the water vapour surrounds the leaf and does not move away.
how does humidity affect transpiration rate
the drier the air around the leaf, the faster transpiration happens.
how are guard cells adapted to open and close stomata
1) they have a kidney shape which opens and closes the stomata
2) when the plant has lots of water the guard cells fill with it and go plump and turgid.
3) this makes the stomata open so gases can be exchanged for photosynthesis
4) when the plant is short of water, the guard cells lose water and become flaccid, making the stomata close. this helps stop too much water vapour escaping
5) thin outer walls and thickened inner walls make the opening and closing work
6) they are also sensitive to light and close at night to save water without losing out on photosynthesis
7) you usually find more stomata on the undersides of leaves than on the top. the lower surface is shaded and cooler - so less water is lost through the stomata than if they were on the upper surface
8) guard cells are therefore adapted for gas exchange and controlling water loss within a leaf.
