2. Function of leaves: Leaf Structures: Wide variety of shapes and sizes - important feature in plant identification Blade: Broad, flat portion of leaf Primary site of photosynthesis Site of transpiration Site of gas exchange - Site of most photosynthesis Petiole: Stalk like region on leaf where it is attached to stem

3. Three Tissue Layers: 1. Epidermis layer: usually 1 cell layer thick - On top and bottom of leaf - impermeable cuticle (top & bottom) - H 2 O, O 2, & CO 2 enter & exit through stomata (bottom) Upper Epidermis Lower Epidermis CO 2 O2O2 LEAF CS **Label Your Leaf CS**

4. 2.Mesophyll Layer: Organized into two layers a. Palisade Mesophyll - Lays directly beneath upper epidermis - Site of most photosynthesis - Made up of columnar cells & are tightly packed into one or two layers LEAF CS Palisade Mesophyll Mesophyll

5. b. Spongy Mesophyll: - Beneath palisade layer - Irregularly shaped cells (balloons) LEAF CS MesophyllSpongy Mesophyll All the Black Space is AIR!!! -surrounded by large air spaces for diffusion: O2, CO2, and H2O

6. 3. Vascular Layer: - Consists of vascular bundles called veins (circular) - Continuous with vascular bundles in stem & petiole - Veins branch repeatedly so each cell is less than 1mm from a vein. Xylem (top) Phloem LEAF CS

7. Venation in Monocots and Dictos: Arrangements of veins in a leaf - Monocots: Parallel venation - Ex: grasses - Dicots: Net Venation - Ex: maple

8. Leaf Processes: 1.Transpiration: Evaporation of water in plant through stomata which increases absorption at roots 2.Gas Exchange: Exchange of CO 2 and O 2 through stomata Stomata: Bordered by 2 kidney shaped guard cells -Modified epidermis cells that regulate H 2 O and gas exchange - Contain chloroplasts - Open during day, closed during night - Found in lower epidermis **Write Small!!!**

9. Stomata in monocot and dicot leaves: Monocots: Parallel Dicots: Random LEAF CS Stomata

10. 3.Photosynthesis: Process by which chlorophyll and enzymes in leaves convert certain wave lengths of light to chemical energy

11. Simple equation of photosynthesis: Sunlight + CO 2 + H 2 O Carbohydrates + O 2

12. Chloroplasts: Sacks that contain photosynthetic pigments - Site of photosynthesis Thylakoids: Series of flattened sacks - Acts like solar panels to collect sun energy Grana: Stacks of thylakoids Stroma: Liquid solution which contains 4 pigments - Surrounds grana

13. Carotenes ORANGES Spring/Summer: only green is reflected = SEE all other colors hidden Fall Colors: Chlorophyll is all used up, see other reflected pigments Chromatography: technique used to separate a mixture into its different components 2 Other Pigments: Xanthophylls YELLOWS Chlorophyll: 1) Chlorophyll A = 95% 2) Chlorophyll B = 5%

14. ROYGBIVROYGBIV 700nm400nm = White Light (prism) eded rangerange ellowellow reenreen luelue ndigondigo ioletiolet

15. Uses of Leaves in Plant Identification  1. Arrangement of leaves on stem  2. Divisions in a leaf  3. Shape  4. Character of leaf margin  5. Veins