B2.2.6 Flashcards
what is a potometer
A potometer is a device used to measure the rate of transpiration
How does the potometer measure the rate of transpiration
It measures the rate of transpiration by how quickly the bubble in the capillary tube moves
What increases the rate of transpiration
Anything that increases the rate of photosynthesis increases the rate of transpiration. This is because the stomata open to allow more CO2 into the plant. As a result the plant loses more water by evaporation.
How does light intensity affect the rate of transpiration
Stomata open in the light and close in the dark. If you increase light intensity more evaporates. The rate of transpiration increases until all stomata are open. Transpiration is now at its maximum rate.
How does temperature affect the rate of transpiration
If you increase the temperature, water evaporates more quickly from leaf cells. Increase concentration gradient leads to an increased rate of diffusion leading to an increased rate of transpiration
How does air movement affect the rate of transpiration
When air moves over the surface of leaf, it moves evaporated water molecules away from the leaf. The faster the air moves, the faster the water molecules are moved. This increases the concentration gradient between the leaf and the air as fewer water molecules are present in the air surrounding the leaf, compared to the inside of the leaf. This means that water diffuses more quickly out of the leaf.
How does humidity affect the rate of transpiration
Humidity is the amount of water in the air. The higher the humidity, the more water it contains. If you decrease the humidity, this increases the concentration gradient between the leaf and the air so water diffuses out more quickly. This increases the rate of transpiration.
