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
Fraser fir
Red pine
Douglas fir
White pine
Scotch 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
Black locust
Elm
White
birch
Honey locust
beech
Red maple
Crimson king
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
Characteristics/I
D
Leaf Characteristics-Deciduous
1. Leaf arrangement: whorl, alternate,
opposite
2. Leaf type: simple or compound
3. Leaf margin: entire, lobed, toothed–
others exist
4. 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
• Only one leaf blade
• Joined by its stalk to the
woody stem
• Examples: maple, oak,
aspen, beech
Compound
• 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
forward
3. 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 Structure
Tip
Margin
Blade
Vein
Spine
Midrib
Base
Petiole
External Leaf Parts
1. The large broad part of a leaf is the leaf
blade
 Large 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 plant
 Water 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.
External Leaf Parts
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)
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
Cuticle
Palisade
Epidermis
Chloroplast
Vein
Xylem
Spongy
Layer
Phloem
Air Space
Guard Cell
Stoma
Cuticle
Epidermis
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