LEAVES

Coniferous VS Deciduous

Which is Which?

Characteristics of Conifers

• Needle shaped leaves• Seeds that develop

inside cones• Evergreen – green

year round• Gymnosperm, conifer,

softwood• Examples: pine,

spruce, hemlock, fir

Examples of conifers

Balsam fir Douglas fir

Fraser fir Scotch pine

Red pine

White pine

Conifer leaves• Needle like • Scale like

Conifer needles

• Clusters • Singles

Deciduous Tree Characteristics

• Broad flat leaves• Lose all leaves each

year in the fall• Angiosperm

(flowering plants), broadleaf, hardwood

• Examples: oak, maple, beech, aspen, ash

Deciduous examples

Red oak Red maple

Black locustWhitebirch

Crimson king

Honey locust

beech

Elm

Exceptions

• Larch trees have cones and needles, but lose their leaves each year.

• Yew trees have needle shaped leaves and are evergreen but have berries not cones.

• Holly trees have broad flat leaves and it is evergreen.

Leaf Characteristic

s/ID

Leaf Characteristics-Deciduous1. Leaf arrangement: whorl, alternate,

opposite2. Leaf type: simple or compound3. Leaf margin: entire, lobed, toothed–

others exist4. Leaf texture: hairy, waxy, rough, smooth,

thick, thin, etc.5. Leaf shape: ovate, obovate, lanceolate,

cordate, elliptical, etc. – others exist

1.

What is the leaf arrangement?

What is the leaf arrangement?

2. Leaf Type

Simple Compound

• Only one leaf blade• Joined by its stalk to the

woody stem• Examples: maple, oak,

aspen, beech

• Made up of several leaflets

• Leaflets are joined to a midrib that is not woody

• Examples: ash, walnut, sumac

Simple or Compound?

What is the leaf type?

3. Leaf Margins

1. Entire = margin lacks teeth (smooth)2. Serrate = saw-tooth with the teeth pointing forward3. Lobe = projecting part or segment of the leaf

- Space between two lobes is a sinus- Example maple or oak

4. Leaf Texture

hairy, waxy, rough, smooth, thick, thin, etc.

Describe the “leaf” of the aloe plant

5. Leaf Shapes • Ovate = egg-like shape, broadest part below

the middle• Obovate = shaped like an egg, broadest part

above the middle• Lanceolate = much longer than wide• Cordate = shaped like a heart• Elliptical = have an ellipse shape, broadest

part in the middle

External Leaf Structure

External Leaf StructureTip

Margin

Vein

Spine

Midrib

Base

Blade

Petiole

External Leaf Parts

1. The large broad part of a leaf is the leaf bladeLarge surface area for photosynthesis Supported by a system of veins that contain xylem

and phloem

2. Main vein running down the middle is the midrib

Help position the blade in a way that it is facing a light source

External Leaf Parts

3. The leaf blade is connected to the stem by the petiole

Lifeline between the leaf and the rest of the plantWater and minerals flow into the leaf blade and

food flows out of the leaf blade through the petiole

4. The edge of the leaf blade is referred to as the margin

Wavy, toothed, lobed, and entire or smooth.

5. On top of the leaf is a waxy non-cellular layer called the cuticle

Prevents water from escaping Plants in bright arid conditions have thick cuticles to

retain water

6. Veins Contain xylem and phloem (stem cells that

allow for movement of nutrients/waste)

External Leaf Parts

Internal Leaf Structure

Internal Leaf Parts 1. The epidermis is the skin-like layer of cells on the top AND the bottom surface of the leaf– The epidermis may be one or many layers thick– Protective

2. Between the epidermal layers is the mesophyll– Photosynthetic occurs in mesophyll cells– Network of veins containing xylem and phloem tissues– 2 Types:

• Palisade mesophyll – tightly packed cells standing on end directly beneath upper epidermis

• Spongy mesophyll – loosely packed cells, form air spaces to hold products of photosynthesis, under palisade

What are the functions of the internal components of a leaf?

3. Leaves have openings in the epidermis called stomata - singular: stoma- Allow the diffusion of carbon

dioxide, oxygen, and water.- Specialized cells called guard

cells control the opening and closing of the stomata

4. Trichomes- Specialized cells that appear as hairs on the leaves of some plants- Reduce water loss by slowing air movement - Discourage some pests from devouring the

leaves- Example: soybeans

CuticleEpidermis

PalisadeChloroplast

SpongyLayer

Xylem

Phloem

Epidermis

Guard Cell

Stoma

Cuticle

Vein

Air Space

Additional Comments – Internal Structure

• Chloroplast– Organism containing chlorophyll which is green and collects

light energy• Xylem– Transports water and nutrients up the plant

• Phloem– Transports sugars down the plant

• Guard Cell– Controls moisture and gas exchange– Open when plant is well watered and closed when the plant

is dry