B3 - Stomata Flashcards
What’s the plural of stoma
Stomata
What are stomata?
Tiny pores on the surface of a plant which allow CO2 and O2 to defuse directly in and out of a leaf
They also allow water vapour to escape during transpiration.
How do stomata controls the amount of water lost from the leaves?
They open and close because of guard cells
What are the cells that surround the stomata?
Guard cells
What does turgid
Swollen with water.
What does flaccid mean?
Low on water and limp.
When guard cells are turgid what are the stoma like?
Open
When the flaccid what are the stoma like?
Shut
What happens to the stomata when there is a water shortage?
They automatically close.
How and why do stomata close at night?
They are sensitive to light.
To save water without losing out on photosynthesis.
What is pumped into guard cells in responding to stimuli like light?
Potassium ions (K+)
What happens when potassium ions are pumped into guard cells?
The solute concentration of the guard cells increases which decreases the concentration of water molecules.
Water then moves into the guard cells by osmosis this makes the guard cell turgid and the stoma opens.
What happens when potassium ions leave the guard cells?
The concentration of water molecules in the cell increase.
Water then moves out due to osmosis. The guard cells become flaccid and the stoma closes
Describe what has happened inside a cell that is said to be palsmolysed?
When a plants really short on a water the cytoplasm inside it’s cells starts to shrink and the membrane pulls away from the cell wall.
Explain how the stomata open in response to light. (4 marks)
Potassium ions are pumped into guard cells in response to light (1 mark)
This increase the solute concentration of water molecules (which decreases the concentration of water molecules) (1 mark)
Water then moves into the guard cells by osmosis (1 mark)
This makes the guard cells turgid and the stoma opens (1 mark)
