1. Photosynthesis
and
Leaf Structure

2. Parts of a Plant Leaf: where photosynthesis occurs
Stem: support system to hold plant upright
Roots: takes in water from the soil

3. Why are leaves GREEN?

4. Photosynthesis occurs in the Leaf
Leaf has a large surface: lots of chloroplasts & chlorophyll
Can capture a lot of sunlight

5. Gas Exchange Happens at the Leaf
Stomates: holes in the bottom of the leaf that allow Carbon Dioxide (CO2) in and Oxygen (O2) out
Stomates

6. Water loss Happens at the Leaf
Transpiration: Plant “sweat”, leaves plants through their stomates
Stomates

7. Guard Cells control the Stomates
Each stomate is surrounded by 2 guard cells
Guard Cells: control if the hole is open or closed
Can prevent water loss!
Guard Cells

8. Guard Cells Guard Against water Loss
Closed Stomate -
Water is not lost
Open Stomate -
Allows water out & gases
in and out

9. stomate
guard cells
epithelial cells

10. Challenge! On notebook paper
In some land plants, guard cells are found only on the lower surfaces of the leaves. In some water plants, guard cells are found only on the upper surfaces of the leaves. Explain how guard cells in both land and water plants help maintain homeostasis. In your answer:
• identify one function regulated (controlled) by the guard cells in leaves
• explain how guard cells carry out this function
• give one possible advantage of the position
of the guard cells on the leaves of land plants

11. Challenge!
• identify one function regulated (controlled) by the guard cells in leaves
• explain how guard cells carry out this function
• give one possible advantage of the position
of the guard cells on the leaves of land plants