Transcript Blade - Warren County Public Schools

Plant Anatomy
Section 3: the leaf
Terms
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Photosynthesis
Epidermis
Cuticle
Stoma
Transpiration
Guard Cells
Mesophyll
Palisade Layer
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Spongy Mesophyll
Palisade Mesophyll
Blade
Margin
Petiole
Simple Leaves
Compound Leaves
Function of Leaves
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Responsible for the
production of food in the
plant.
Photosynthesis
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The ability for green
plants to convert solar
energy into chemical
energy.
produces oxygen and
water.
(Chlorophyll)
CO + H O = C H O + O + H O
2
2
6
(light)
12
6
2
2
Parts of a Leaf
 1.
Tip or apex – this is the top of the leaf
Margin – is the edge of the blade; This
is quite specific to each species of plant
 2.
Midrib – the central vein running down
the center of the blade
 4. Veins – contain the xylem & phloem of
the plant
 3.
Parts of a Leaf
Base – is found at the bottom of the
blade
 5.
 6.
Petiole –hold xylem & phloem;
Blade – the main collecting structure of
the leaf
 7.
Main Parts of a Leaf
Tip/Apex
Midrib
Blade
Margin
Leaf
Veins
Base
Petiole
Types of Leaves.
 Some

are adapted to hot, dry climates
They store water in their leaves or are smaller
in size
 Some
have very large blades to collect
maximum light in shady locations
 Some plants have their blades broken into
many sections
Types of a Leaf

A leaf which has only
one blade on its
petiole is called a
simple leaf
 Most
plants have
simple leaves

When the blade is
divided into three or
more sections, it is
said to be a
compound leaf
 There
are many
different kinds
Types of Compound Leaves
Odd
Pinnately
Compound
Even
Pinnately
Compound
Palmately
Compound
Vein Patterns

Veins of flowering plants are found in
several patterns
 Most
patterns can be categorized into two
main groups
 A. Parallel veins – found in monocots
None of the veins on the whole leaf will cross each
other
 It may look like they fuse together at the top or
bottom of the blade

Veins (cont.)
 B.
Netted veins – found in dicots
They connect & branch from each other
 Some have several smaller veins branching out
of a dominant midrib
 Other leaves have several dominant veins
(midribs) branching from the petiole
 A few have a spreading vein pattern called
dichotomous venation
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
Seen in the Ginkgo tree
Types of Leaf Venation
Palmately Netted
Veins
Parallel
Netted Veins
Pinnately Netted
Veins
Dichotomous
Netted Veins
Layers of the leaf

Cuticle – on top of the
leaf is a waxy non-cellular
layer
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Prevents water from
escaping the leaf
It is usually very thick on
plants in arid regions


Cacti and Jade plants
have thick cuticles.
Other plants tend to have
hair in addition to a cuticle.

Helps to prevent water
loss.
The Epidermis
Epidermis – the next
layer of the leaf
The Stoma

Stomata – Pores and openings on the
epidermis
 Allow
exchange of oxygen, carbon dioxide
and water vapor “breathe”

Movement of water vapor through the stoma is
called transpiration.
cells – control the opening & closing
of the stomata
 Guard
Found on either side of the stomata
 Open during the day or raining
 Closed at night and during water stress.
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Internal Parts of A Leaf
Petiole
Blade
Cuticle
Upper Epidermis
Palisade Mesophyll
Vein
Spongy Mesophyll
Lower Epidermis
Air
Spaces Stomata
Stoma, singular
Guard Cell
Leaf Appearance
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Pigments determine the
color of leaves.
Most plants are bought
for their colors and
vegetative patterns.
Texture play a major role
in the attractiveness of
class.
Chlorophyll
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The major pigment in all
plants.
Major component in the
photosynthetic process.
Give plants their green
color.
Most of the time plant will
have other pigments but
chlorophyll overrides the
other pigments
Other Pigments
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Carotene- produces yellow/ orange colors
 Carrots
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Xanthophyll- yellow to no color at all
Anthocyanins- blue, purple, and red
Flavonols- yellow and crème colors.
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Anthocyanins and flavonols have a bigger impact on flowers
than in leaves.
Variegation- plants that have different color
patterns.
Patterns / Textures

Bracts: Modified leaves
that take pedal like
appearance.

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Poinsettia
Texture is important to
aesthetical appeal
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Texture factors include:
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Size of the leaf
Margin of the leaf
Surface