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?

Agenda

Do NowPhotosynthesis review questionsGuard Cell notesVideo

Practice QuestionsIn the overall equation for photosynthesis, six

molecules of carbon dioxide result in six molecules of

a. glucose.b. water.c. oxygen.d. ATP.

Practice QuestionsIn the overall equation for photosynthesis, six

molecules of carbon dioxide result in six molecules of

a. glucose.b. water.c. oxygen.d. ATP.

a. thylakoids.

b. chloroplasts.

c. plant cells.

d. all of the above

The stroma is the space that surrounds

a. thylakoids.

b. chloroplasts.

c. plant cells.

d. all of the above

The stroma is the space that surrounds

  If carbon dioxide is removed from a plant’s environment, what would you expect to happen to the plant’s production of high-energy sugars?

a. More sugars will be produced.

b. Fewer sugars will be produced.

c. The same number of sugars will be produced but without carbon dioxide.

d. Carbon dioxide does not affect the production of high-energy sugars in plants.

  If carbon dioxide is removed from a plant’s environment, what would you expect to happen to the plant’s production of high-energy sugars?

a. More sugars will be produced.

b. Fewer sugars will be produced.

c. The same number of sugars will be produced but without carbon dioxide.

d. Carbon dioxide does not affect the production of high-energy sugars in plants.

What is the role of RuBP in the light independent reactions?

A. It reduces the 6-carbon molecule and forms 2 G3Ps

B. It provides the chemical energy for the regeneration step

C. It is what carbon dioxide is fixed on to in the first step of the Calvin cycle

D. It is one of the enzymes in the regeneration step

What is the role of RuBP in the light independent reactions?

A. It reduces the 6-carbon molecule and forms 2 G3Ps

B. It provides the chemical energy for the regeneration step

C. It is what carbon dioxide is fixed on to in the first step of the Calvin cycle

D. It is one of the enzymes in the regeneration step

It takes 3 molecules of ATP every turn of the Calvin cycle. How many molecules of ATP does it take to fix enough carbon for a 6 carbon molecule like glucose?A. 9B. 18C. 27D. 54

It takes 3 molecules of ATP every turn of the Calvin cycle. How many molecules of ATP does it take to fix enough carbon for a 6 carbon molecule like glucose?A. 9B. 18C. 27D. 54

Remember

Plants lose water via transpiration

This 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

Regulation of the guard cells

17

Guard 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

Regulation of guard cells

18

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

19

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