The Leaf of a Flowering Plant

Factory of Photosynthesis

Leaf Functions

Carries on PhotosynthesisStores foodLimited capability of reproductionRegulates transpiration.

External Leaf Anatomy

Blade: The flattened part of the leaf.

Margin: The edge of the blade.

Petiole: Connects the blade with the stem.

Vein: xylem, phloem, and connective tissue.

Leaf Type

Simple Leaf: The blade is one complete structure.

Compound Leaf: The blade is divided into smaller units called leaflets.

Leaf Venation

Netted: One main vein with many branching ones off to the sides. (Dicots)

Parallel: Many main veins running along the length of the blade. (Monocots)

Margin

Internal Leaf Anatomy

Epidermis Cuticle Palisade Mesophyll

(chloroplasts) Spongy Mesophyll Vein (xylem and phloem) Air Spaces Lower Epidermis Stomata Guard cells

Upper Epidermis

Palaside Mesophyll

Phloem

Stoma Guard Cells

Air Space

Xylem

Stomata

Guard cells regulate the size of the stoma.

K+ (potassium ions) enter the cells causing them to fill with water.

This opens the stoma when they become turgid.

A loss of K+ causes the opposite to occur, and they close when they become flaccid.

Stomata Control

OpenThe Cells are Turgid

Closed The Cells are Flaccid