Characteristics of Twigs and leaves

Along withLeaf Structures

7TH GRADE SCIENCE

GENERAL TERMS• leaf — a lateral outgrowth from the stem whose

primary function is the manufacturing of food

• twig -- a young woody stem to which leaves and buds are attached

• branch -- a thicker, older woody stem to which twigs are attached

• trunk -- the main vertical stem of a treefruit — the seed-bearing portion of a plant

• deciduous — trees on which all leaves fall at the end of every season of growth

• evergreen — trees on which leaves remain attached for more than one year

twigs

Parts of a twig

• Petiole

• Node

• Internodes

• Lateral/axillary bud

• Terminal bud

• Terminal bud Scars

• Leaf Scar

Petiole

• A leaf stalk, it attaches the leaf to the stem.

Node the place on a

twig where a leaf is attached

Internodethe part of a twig between two nodes

Node

Internode

Lateral/axillary Bud• a bud that is

situated along the sides of a branch and not at the tip

• It may become next years branches or flowers

Terminal bud

• a bud that is at the tip of a stem or branch

• Where the branch can grow longer

Terminal Bud Scars

• Can determine the age of the

twig by counting these

Leaf/Bud Scar

• the scar left on a twig when a leaf falls

Leaves

Functions of Leaves

• Manufacture food for the plant, through process of photosynthesis

Equation for Photosynthesis: CO2 + H2O C6H12O6 + O2

Photosynthesis only occurs when light is present

Leaf Terms• Epidermis: outside layer of the

leaf (leaf surface)

• Stomata: openings in the leaves where carbon dioxide comes in from the atmosphere (needed for photosynthesis)

Leaf Terms

• Transpiration: the loss of water vapor from the plant; most water is lost from the stomata, some through the cuticle layer.

Parts of a Leaf

•Lamina/blade

•Leaf Apex

•Midrib

•Petiole

•Stem

•Vein

Lamina/blade

• The blade of the leaf.

Leaf Apex

• The outer end of a leaf; the end that is opposite the petiole.

Midrib

• The central rib of a leaf, it is usually continuous with the petiole.

Petiole

• A leaf stalk, it attaches the leaf to a plant.

Stem

• The main support of the plant, also called the apex.

Vein• One of the many

vascular structures on a leaf. Veins provide support for the leaf, and transport both water and food through the leaf.

Veins

• Parallel– Up and down

• Palmate– From one central

location

• Pinnate– Off one main vein

Types of Leaves

• Simple

• Compound

Simple

• Simple Leaves are of one continuous leaf surface, not divided into separate segments.

Compound

• Compound leaves are composed of many smaller leaflets, each resembling a complete leaf in and of itself.

Types of Compound Leaves

• Palmate

• Odd Pinnate

• Even Pinnate

Palmate

• The leaflets are attached at one plane at the base.

Odd Pinnate

• Leaflets are on two opposite sides of the axis, with an odd number of leaflets, one at the tip.

Even Pinnate

• Leaflets are on two opposite sides of the axis, with an even number of leaflets, and paired at the tip.

Leaf Arrangement

• Alternate

• Opposite

• Whorled

Alternate

• Leaves are borne singly at each node.

Opposite

• Leaves are borne two at each node.

Whorled

• Three or more leaves are arranged in a circle around the stem.

Leaf Shape

• Heart

• Lance

• Oval

• Diamond

• Round

Heart Shaped

• The top of the leaf is pointed while the bottom of the leaf is uneven. Making a heart like shape.

Lance shaped

• Long and narrow

Oval shaped

• Have a rounded top and bottom.

Diamond Shape

• The tip is pointed while the base is rounded

Round shaped

• Completely rounded at the top and bottom

Leaf margins

• Smooth/entire

• Wavy

• Serrate (saw toothed)

• Doubly serrate

• lobed

Smooth/entire margin

• no kind of marginal division or nearly lacking marginal division

Wavy margin

• having a wavy up and down edge

Toothed (serrate) Margin

• having sharp, straight-edged teeth pointing to the apex

Double serrate margin

• primary teeth have smaller secondary teeth

Lobed Margins

• With Shallow, obtuse or rounded teeth scalloped