Leaves have several key parts that allow them to efficiently perform photosynthesis. The blade is the main structure that collects sunlight, while the petiole attaches the blade to the stem. Within the blade are a midrib and veins that transport water and nutrients. The edge of the leaf is called the margin. A simple leaf has one continuous blade, while a compound leaf's blade is divided into sections. The four main types of venation patterns are parallel, pinnately netted, palmately netted, and dichotomous. Gas exchange occurs through stomata on the lower epidermis, which are controlled by guard cells.

1. Lesson 4 Understanding Leaf Anatomy And Morphology

6. Main Parts of a Leaf Tip/Apex Midrib Margin Veins Base Petiole Blade Leaf Courtesy of Corinne Banowski

9. Types of Compound Leaves Odd Pinnately Compound Even Pinnately Compound Palmately Compound Courtesy of Wm. C. Brown Publishers

12. Types of Leaf Venation Parallel Netted Veins Pinnately Netted Veins Palmately Netted Veins Courtesy of Wm. C. Brown and McGraw Hill Publishers Dichotomous Netted Veins

16. Internal Parts of A Leaf Petiole Blade Cuticle Upper Epidermis Palisade Mesophyll Vein Spongy Mesophyll Lower Epidermis Guard Cell Stomata Air Spaces Stoma, singular Courtesy of Wm. C. Brown Publishers