Topic 2 Transpiration And stomata Flashcards
What effects transpiration rate
Light intensity
Temperature
Air flow
Humidity
How does light intensity affect transpiration rate
The brighter the light, the greater the transpiration rate
When does the stomata close
Begins to close as it get dark
Photosynthesis can’t happen in the dark so they don’t need to be item to let CO2 in
When closed very little water can escape
How does temperature affect transpiration rate
The warmer it is the faster the transpiration happens
When it’s warm the water particles have more energy to evaporate and diffuse out of the stomata
How does the air flow affect the transpiration rate
The better the air flow around the leaf the greater the transpiration rate
What happens if air flow around the leaf is poor
The water vapour just surrounds the leaf and doesn’t move away
This means there is a high concentration of water particle outside the leaf as well as inside it so the diffusion doesn’t happen as quickly
What happens if there is a good air flow around the leaf
The water vapour is swept away maintaining a low concentration of water in the air outside the leaf.
Diffusion then happens quickly from an area of high concentration to an area of lower concentration
How does humidity effect transpiration
The drier the air the faster the transpiration
If the air is humid there’s isn’t much difference between water vapour in plant so diffusion won’t happen quickly
How can you estimate the rate of transpiration
Measure the uptake of water by the plant . This is because you can assume that water uptake by the plant is directly related to water loss by the leaves (transpiration)
Rate of transpiration measurement
Set up a potometer with plant and tap shut off and record the starting position of the air bubble
Start a stop watch and record the distance moved by the bubble per unit time
Keep the conditions constant throughout the experiment
What’s open and close the stomata 
Guard cells
What happens to the guard cells of a plant if it has lots of water
The guard cells filled it and go plump and turgid
What happens when the guard cells go plump
Makes the stomata open so gases can be exchanged for photosynthesis
What happens to the guard cells in a plant is short of water
The guard cells lose water and become flaccid making the stomata close and helps stop too much water vapour escaping
What are the walls like of the stomata
Thin outer walls and thickened inner the walls make the opening and closing work
