Photosynthesis

§Food supply factory §Adapted to maximize light absorption and CO 2 diffusion.

§Cuticle – waxy waterproof barrier l Protects leaf §Epidermal Cells – protects the leaf §Mesophyll Layer

§Area of photosynthesis §Loaded with chloroplasts §Pallisades Layer – Tall columnar shaped cells  Spongy Layer – Has lots of air spaces between the cells

 Air sacs act as reservoirs for CO 2 and H 2 O.

Chloroplasts §Major site of photosynthesis §Leaves have the most chloroplasts l About a ½ million per square millimeter

Chloroplast Structure §Has an outer and inner membrane §Stroma: thick fluid inside chloroplast l Where sugars are made §Thylakoids:Interconnected sacs in stroma l Where chlorophyll is l Houses machinery that converts light energy to chemical energy §Grana:Stacks of thylakoids

§Chloroplasts of plant cells capture light energy that has traveled 150 million km from the sun. §They convert the energy from the sun into chemical energy that is stored in sugar and other organic molecules

The location and structure of chloroplasts Leaf Cross Section Leaf Mesophyll Cell Mesophyll VeinStoma CO 2 O2O2 Chloroplast GranaStroma TEM 9,750X Stroma Granum Thylakoid space Outer membrane Inner membrane Intermembrane space LM 2,600X

§Xylem – transports water  Phloem – transports nutrients

§Stoma; Stomata: Regulates water loss and carbon dioxide intake §Guard Cells: Specialized cells that surround the stoma l Controls the opening and closing of the stoma §Both are found in the epidermis