1. Functioning of Guard Cells

2. I. Guard Cells
A. Function – to balance water loss and need for photosynthesis
1. control diameter of stomata

3. II. Guard Cell Structure
A. Thicker cell wall toward center
B. Cellulose microfibrils causes outward buckling when cell is turgid(full of water)

4. III. Closing
A. Cells lose water (become flaccid)

5. IV. Opening A. Cells swell as water moves in by osmosis
1.stomate diameter increases

6. V. Changes take place when K concentration changes
A. Potassium from vacuole enters guard cell when opening
1. Active transport
2. Water enters by osmosis
3. Active transport of H+ helps drive K into the cell
B. Potassium leaves guard cell when closing

7. VI. Aquaporins – proteins that regulate water movement through membranes are involved

8. VII. Light by increasing photosynthesis is involved
A. Creates more ATP for active transport

9. VIII. Low carbon dioxide concentration causes opening

10. IX. Biorythms