Week 14 L6: Abiotic Environment - Water Stress - Stoma Closure Flashcards
Where are the receptors for ABA found?
stomata/stoma
What are the receptors called that ABA bind to?
pyrabactin-like proteins
What is pyrabactin?
synthetic sulfonamide which is a synthetic agonist for ABA.
What does ABA to pyrabactin-like channels cause?
Causes a signalling mechanism which activates calcium channels, which brings Calcium from outside and calcium stored in the vacuole into the cytoplasm.
Calcium moves into the cytoplasm but where does it cone from?
vacuoles and outside the cell via Ca2+ channels
What happens to intracellular calcium conc upon Ca2+ channels opening?
elevated conc
What happens when Ca2+ levels are elevated in the cell?
inhibits proton pumps. so H+ remains inside the cell.
What is the effect when proton pumps are inhibited?
increase H+ conc in the cell. increase acidity, lower pH
What happens when the cell becomes more acidic?
K+ channels are blocked.
So no K+ will enter the cell.
What happens simultaneously to K+ channels pumping K+ into cell being blocked?
K+ channel which pump K+ out of the cell are activated
What does the Ca2+ in the cytoplasm lead to?
H+ pump being inhibited, decrease pH and block K+ coming into the cell
It directly activates K+ channels which pumps K+ out of the cell.
What accumulates outside the cell?
K+ and water leaves the guard cell.
Why does water move outside the cell?
Due to a drop in water potential outside the cell
When does the guard cell close?
When water leaves the cell
What are the rigidified part of the guard cells?
lips
