Overview of Leaves

Number of Leaves per Tree 1) 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.

Continued 4) 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).

Continued 7) 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 Structures 1) Consists of a flat broad blade and a stem 2) Stem-like petiole that attaches the blade to the stem. 3) Simple leaves have one undivided blade per petiole.

Continued 4) 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) Dermal b) Ground c) Vascular

Continued 7) 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.

Continued 8) 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

Continued 10) 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.

Continued 3) 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.

Wood 1) Uses : furniture, tool handles, toys, houses 2) Products : include: paper, drugs, fuel, charcoal, even glaze on donuts 3) Various kinds of wood differ in color, grain, hardness and texture depends on the kind of tree its cut from.

Continued 4) 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