Transcript Plant Science Unit Leaves

Characteristics of
Twigs and leaves
Along with
Leaf 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
• Terminal bud
• Node
• Terminal bud
Scars
• Internodes
• Leaf Scar
• Lateral/axillary
bud
Petiole
• A leaf stalk,
it attaches
the leaf to
the stem.
Node
the place on a
twig where a
leaf is attached
Node
Internode
Internode
the part of a
twig between
two nodes
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
• Petiole
• Leaf Apex
• Stem
• Midrib
• 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
• Diamond
• Lance
• Round
• Oval
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