1. Cross Section of a Leaf

2. Stoma Open vs. Closed  Open – w/light & when guard cells filled with water  Closed – w/o light & when guard cells lacking water (dehydrated)  Why is it important to have stomata open? Closed vs. Open

3. Stomata Open vs. Closed Water No Water Light Dark

4. How many stomata ? High light : more stomata Low light : less stomata (less photosynthesis) Dicots (Webbed veins) more stomata lower leaf Monocots (Parallel veins) same amount both sides Water plants : none on bottom, always open Desert : limited stomata, open at night (adaptation)

5. Why is it important to have stomata open? GAS EXCHANGE for photosynthesis!

6. Capillarity Action/Transpiration  Cohesion &adhesion draw water - capillary action.  Water travels from roots, up stem & throughout leaves via xylem  Water enters the guard cells ( Ψ)  Water evaporates to atmosphere (transpiration)

7. How Does Osmosis determine if the Stomata are open or closed?

8. Osmosis due to hypertonic and hypotonic environments!

9. Guard Cells/Stomata