Plant Anatomy Section 3: the leaf

Terms Photosynthesis Epidermis Cuticle Stoma Transpiration Guard Cells Mesophyll Palisade Layer Spongy Mesophyll Palisade Mesophyll Blade Margin Petiole Simple Leaves Compound Leaves

Function of Leaves Responsible for the production of food in the plant.

Photosynthesis The ability for green plants to convert solar energy into chemical energy. produces oxygen and water.

(Chlorophyll) CO 2 + H 2 O = C 6 H 12 O 6 + O 2 + H 2 O (light)

 1. Tip or apex – this is the top of the leaf  2. Margin – is the edge of the blade; This is quite specific to each species of plant  3. Midrib – the central vein running down the center of the blade  4. Veins – contain the xylem & phloem of the plant Parts of a Leaf

 5. Base – is found at the bottom of the blade  6. Petiole –hold xylem & phloem;  7. Blade – the main collecting structure of the leaf Parts of a Leaf

Main Parts of a Leaf Tip/Apex Midrib Margin Veins Base Petiole Blade Leaf

Types of Leaves.  Some are adapted to hot, dry climates They store water in their leaves or are smaller in size  Some have very large blades to collect maximum light in shady locations  Some plants have their blades broken into many sections

Types of a Leaf A leaf which has only one blade on its petiole is called a simple leaf  Most plants have simple leaves When the blade is divided into three or more sections, it is said to be a compound leaf  There are many different kinds

Types of Compound Leaves Odd Pinnately Compound Even Pinnately Compound Palmately Compound

Vein Patterns Veins of flowering plants are found in several patterns  Most patterns can be categorized into two main groups  A. Parallel veins – found in monocots None of the veins on the whole leaf will cross each other It may look like they fuse together at the top or bottom of the blade

 B. Netted veins – found in dicots They connect & branch from each other Some have several smaller veins branching out of a dominant midrib Other leaves have several dominant veins (midribs) branching from the petiole A few have a spreading vein pattern called dichotomous venation  Seen in the Ginkgo tree Veins (cont.)

Types of Leaf Venation Parallel Netted Veins Pinnately Netted Veins Palmately Netted Veins Dichotomous Netted Veins

Layers of the leaf Cuticle – on top of the leaf is a waxy non-cellular layer  Prevents water from escaping the leaf  It is usually very thick on plants in arid regions Cacti and Jade plants have thick cuticles.  Other plants tend to have hair in addition to a cuticle. Helps to prevent water loss.

The Epidermis Epidermis – the next layer of the leaf

The Stoma Stomata – Pores and openings on the epidermis  Allow exchange of oxygen, carbon dioxide and water vapor “breathe” Movement of water vapor through the stoma is called transpiration.  Guard cells – control the opening & closing of the stomata Found on either side of the stomata Open during the day or raining Closed at night and during water stress.

Internal Parts of A Leaf Petiole Blade Cuticle Upper Epidermis Palisade Mesophyll Vein Spongy Mesophyll Lower Epidermis Guard CellStomata Air Spaces Stoma, singular

Leaf Appearance Pigments determine the color of leaves. Most plants are bought for their colors and vegetative patterns. Texture play a major role in the attractiveness of class.

Chlorophyll The major pigment in all plants. Major component in the photosynthetic process. Give plants their green color. Most of the time plant will have other pigments but chlorophyll overrides the other pigments

Other Pigments Carotene- produces yellow/ orange colors  Carrots Xanthophyll- yellow to no color at all Anthocyanins- blue, purple, and red Flavonols- yellow and crème colors. Anthocyanins and flavonols have a bigger impact on flowers than in leaves. Variegation- plants that have different color patterns.

Patterns / Textures Bracts: Modified leaves that take pedal like appearance.  Poinsettia Texture is important to aesthetical appeal  Texture factors include: Size of the leaf Margin of the leaf Surface

Summary/ Review Why is Photosynthesis Important?  Source of all life What is the job of the stoma?  Allow the plant to “breathe” What influence the attractiveness of the leaf? What is the major pigment in plants?