1. SBI3U Day 4 – Leaf Structure and Function

2. 3 Functions of Leaves Trap light energy for photosynthesis
Production of sugar from photosynthesis
Exchange of gases – oxygen and carbon dioxide

3. Wide - Helps to catch more light energy
Thin - Help get carbon dioxide from bottom to top of leaf for photosynthesis

4. Leaf Stucture

5. 3 Main Structural Regions
Epidermis: modified cells, hairs, waxy cuticles or guard cells
Mesophyll : has an upper palisade mesophyll (long, thin cells that are perpendicular to the epidermis) and a lower spongy mesophyll (large air spaces in between these cells so that the exchange of gases could occur). These are the specialized cells where photosynthesis occurs. THESE CELLS CONTAIN CHLOROPLASTS.
Veins: form a network through the leaf, contain xylem (conducts water) and phloem (conducts food).

6. cuticle: a waxy secretion of epidermis. unction is water proof barrier
epidermis: clear, no chloroplasts, protection,
lower epidermis = more
palisade mesophyll:
parenchyma cells, lots of chloroplasts
maximum photosynthesis
horizontal = max exposure to the light,
spongy mesophyll :
parenchyma cells, lots of air spaces
access to outside of leaf (via stomata) area of gas exchange
veins : xylem on top, phloem below
surrounded by sclerenchyma cells
guard cells: in pairs
holes created = stomata
CO2 enters, O2 released
only cells of the epidermis containing chloroplasts

8. Stomata and Guard Cells
Light: Stomata open in the presence of light and close in darkness.
Temperature:
Rise = open
Fall = closed
Water availability:
Water stressed (less water available to plant and high transpiration rate) = closed
Mechanical shock:
Causes stomatal closure.
Oxygen
Carbon dioxyde

9. A Few Video Clips Leaf Structure Review Adaption to Extremes
Jungle Adaptations

10. Home Work
Pg 540 # 5, 6, 9, 10