please do now: 1) define transpiration 2) what excites the electrons (and starts them along the...
TRANSCRIPT
AIM: SWBAT explain how stomata open and close
Please Do Now: 1) Define transpiration2) What excites the electrons (and starts them along the electron transport chain) during the
light dependent reactions?
AgendaDo NowGuard Cell notesVideoWork on photosynthesis study sheet
RememberPlants lose water via
transpirationThis is bad because plants
need water for a lot of things
It mostly happens via stomata, little tiny holes in the leaf
Leaves need stomata to let CO2 in and oxygen out during photosynthesis
Water escapes whenever they are open
How do plants minimize their water loss through the stomata?The stomata in plants
are surrounded by guard cells
There are always 2, and they are capable of opening and closing the stomata
It is like opening and closing a door: when closed there is no CO2 coming in, but no water escaping
How do guard cells open and close the stomata?The guard cells are
crescent shaped with thick inner walls and thin outer walls
They are basically like balloons that inflate and deflate to open/close the stomata
How do guard cells inflate/deflate?When the plants
want the stomata to be open, they inflate the guard cells by pumping potassium ions (K+) into the cells
Osmosis then draws water into the cells and inflates them to their full crescent shape
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Regulation of the guard cellsGuard cells flaccid
Stoma closed
K+
K+
K+
K+
K+K+
K+
K+
K+
K+K+
K+
K+ ions have the same concentration in guard cells and epidermal cells (the surrounding cells)
Light activates K+ pumps which actively transport K+ from the epidermal cells into the guard cells
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Regulation of guard cells
K+K+
K+
K+
K+K+
K+
K+
K+
K+K+
K+
Increased concentration of K+ in guard cells
Lowers the concentration of water in the guard cells
Water moves in by osmosis, down osmotic gradient
H2O
H2O
H2O
H2O
H2O
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Stoma open
Guard cells turgid
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
Increased concentration of K+ in guard cells
Lowers the in the guard cells
Water moves in by osmosis, down gradient
H2O
H2O
H2OH2O
H2O
H2O
Summary (fill in the blank on your own)Guard cells are important for
maintaining the balance between ____________________ and _________________________
Summary (fill in the blank on your own)Guard cells are important for
maintaining the balance between gas exchange and water loss