1. A Closer Look at Leaves AP Biology Spring 2011

2. Leaf Structure and Function Variation in leaf types: Eudicot leaves: Simple: undivided, many lobed Compound: blades divided as leaflets Thin, flat blade, which is attached to the stem by means of a stalk, or petiole

3. Leaf Structure and Function Monocot leaves: Flat blades, the base of which forms a sheath around the stem

4. Leaf Structure and Function Evergreens: pants that maintain their leaves throughout the year Deciduous plants: lose their leaves as winter approaches

5. Leaf Structure and Function Leaves are adapted to local environmental conditions Most plants orient their leaves perpendicular to the suns rays to collect energy for photosynthesis Plants growing in hot and dry regions orient their leaves parallel with the suns rays to conserve water and reduce heat absorption

6. Leaf Fine Structure Epidermis: covers all leaf surfaces May be smooth or covered with hairs, scales, or other specializations Has small openings or stomata which allow for gas exchange Waxy cuticle covers epidermis to minimize water loss

7. Leaf Fine Structure Mesophyll: photosynthetic parenchyma Photosynthetic parenchyma cells (in mesophyll layer) are located between the extensive surface areas of the upper and lower epidermis

8. Leaf Fine Structure Mesophyll: CO2 enters through stomata and diffuses through air spaces into the photosynthetic tissue O2 byproduct is released from the plant

9. Leaf Fine Structure Mesophyll: Dicots have two layers of mesophyll The columnar and spongy parenchyma Monocots are not divided into two layers Single layer

10. Veins Veins: the leafs vascular bundles Form a network for water, solutes, and photosynthetic products Eudicots: large veins branch into smaller one embedded in the mesophyll Monocots: veins are similar in length and run parallel with the leafs long axis