Overview of Leaves

Number of Leaves per Tree1) A maple tree can have as many as

150,000 leaves.2) With the combined surface area

greater than 6 basketball courts.3) American Elm can have as many as 5

million leaves.

Continued4) Main Function of Leaves: Trees use

their leaves to trap light for photosynthesis.

5) Photosynthesis – process of making carbohydrates from CO2 and water in the presence of sunlight.

6) A few leaves can also store food ex. Onion (an underground stem, surrounded by thick, fleshy leaves that store food).

Continued7) Leaves also are adapted for other

functions such as protecting some plants from animals and storing water.

8) Leaves useful to humans as sources of dyes, fibers, fuels, drugs, wax, soap, and spices, food, salads.

Leaf Structures1) Consists of a flat broad blade and a

stem2) Stem-like petiole that attaches the

blade to the stem.3) Simple leaves have one undivided

blade per petiole.

Continued4) Compound leaves have more than

one blade per petiole.5) The blades of compound leaves are

called leaflets.6) Leaves contain 3 tissues types (as

stems & roots) :a) Dermalb) Groundc) Vascular

Continued7) Leaf epidermis has 2 special structures

that are adaptations for photosynthesis on land:

A waxy cuticle – a waterproof covering – helps conserve water.

Stomata – are pores in the epidermis; allows CO2 to enter a leaf and water vapor and oxygen to get out

Guard Cells surround stomata.

Continued8) Veins – all leaves contain vascular

tissue The vascular bundles in leaves are called veins.

Transport water and food.

9) Rhizomes – are rhizomes that attached to underground stems. Underground stems that function as roots are called rhizomes

Continued10)Petiole – is the stalk that attaches the

fronds blade to the stem.

2 Patterns of Growth is Seed Plants:1) Primary growth – the elongation of

stems and roots.2) Secondary growth – woody plants

meristem between the xylem and phloem.

This growth of the meristem thickens the plant.

Growth that makes a plant thicker is called secondary growth.

Continued3) Stems have specific places where

leaves are attached.4) Leaves attach to stems at locations

called nodes.5) Nodes – depending on the number of

leaves attached to a stem, the stem may have few or many nodes.

6) Internodes – the section between nodes.

Wood1) Uses: furniture, tool handles, toys,

houses2) Products: include: paper, drugs, fuel,

charcoal, even glaze on donuts3) Various kinds of wood differ in color,

grain, hardness and texture depends on the kind of tree its cut from.

Continued4) Softwoods: trees that are gymnosperms

Usually lack fibers Therefore, the wood is easy to cut and nail making

it popular for construction projects Examples: white pine, redwoods, Douglas fir

5) Hardwoods: are dicot trees Harder, more dense wood Contain fibers Hard to nail Often used to make fine furniture Examples: white oak, teak, sugar maple, ash