Leaf Structure & Function

Leaf Function

A. Photosynthesis
B. Transpiration

 Leaf development and structure

A. Leaf development
1. Leaf primordia initiated in region of apical meristem
2. Primary meristematic tissue: protoderm (epidermis), ground meristem (leaf mesophyll),and procambium (vascular tissue)

B. Leaf structure

1. Epidermis (no chloroplasts, contain cutin and waxes, stomata)

2. Mesophyll
a) All internal leaf tissue (except some vascular tissue)

b) In dicots, usually organized into 2 layers
1) Palisade parenchyma - upper layer
*Elongated cells, perpendicular to leaf surface
* Numerous, large chloroplasts
* Principle photosynthetic tissue of leaf

2) Spongy parenchyma
* Irregularly shaped cells with conspicuous air spaces
* Fewer chloroplasts than palisade layer
* Air spaces important in diffusion of gases
* In monocots - mesophyll is one layer similar to spongy parenchyma

3. Vascular bundles