Form and Structure of Plants
Botany: the study of plants
What is a plant?
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Living organisms which are
eukaryotic and multicellular
Have organized tissues
Have plastids (such as chloroplasts)
Have cell walls containing cellulose
One reason the study of botany
is so important to man is …
Because all the food eaten by man
comes directly or indirectly from
green plants. About 2/3 of the food
we eat comes directly from plants
and 1/3 comes from animals which
eat plants.
Ways Plants are Beneficial:
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Provide most of man's food
Release O2 needed by man and
animals
Plants are raw materials for
many manufactured goods
Plants are a source of beauty
Misconceptions:
All green things are plants.
 All plants
are green.
 All plants
are
autotrophic.

morphology
the shape or form of an organism
Anatomy
the bodily
structure of
an organism
(deals with
how cells and
tissues are put
together)
Types of organs in plants
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Roots
Stems
Leaves
flowers
Flower
Leaf
Root
Stem
Plant organs are determined by
their relationships to nodes
Node:
a region where
a leaf is or was
attached
Plant organs are determined by
their relationships to nodes
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Roots do not have nodes.
Stems have nodes.
Leaves do not have nodes but are
attached to stems at nodes.
Roots
Roots are the organs of
the root system.
A root system is all the
roots of a plant.
Functions of Roots
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Anchors
Absorbs
Transports
Stores food
Two Types of Root Systems
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Taproots
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Fibrous roots
Taproots
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commonly found in
dicots
penetrates the
soil with very
little branching
often stores food
(fleshy roots)
Taproots
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has one or a few
main roots that are
thicker and longer
than the other
roots of the plant
examples: carrots
and dandelions
Fibrous Root System
 commonly
found
in monocots
 have no main
section but
branch out into
the soil in all
directions
Fibrous Root System
 Has
a cluster of
roots that are
approximately
equal in size
 They branch
several times
 Example:
grasses
Types of stems
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Herbaceous stems
Woody stems
Herbaceous stems
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Softer, more flexible
type of stem
Supported by cell
walls and turgor
pressure
Woody plants often
begin as herbaceous
and then become
woody as the grow
older
Woody stems
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Hard and not very
felxible
Capable of
supporting a lot of
weight
Examples: trees
and shurbs
Stem Functions
manufacture,
support, and display
leaves
 conduct materials
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External Structures of Leaves
Margin
Blade: the flat portion
of a leaf
Petiole: the stalk of a
leaf; attaches leaf to stem
Margin: the edge of a
leaf’s blade
Veins: the pipelines that
carry food & water
Node: place on stem
where leaves are attached
External Structures of Leaves
Stipule: a small leaflike or scalelike structure on
a plant that helps to cover a leaf while it is
devleoping
Leaf Venation
Two basic patterns of leaf venation:
• Parallel Venation
• Netted Venation
Parallel Venation
A series of veins which
originate at the stem and
proceeds to the tip of the
leaf
Occurs in monocots – corn,
grass, irises, orchids
Netted Venation
Palmate: two or more main veins
coming from a single point
Examples: maple, ivy, geraniums
Pinnate: if the veins branch off one
large central vein called a midrib
Examples: oaks, apple trees,
African violets
Classification of Leaves
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Simple leaves
Compound leaves
Simple or Compound?
Simple Leaves: one blade on each petiole
Simple or Compound?
Compound: more than one blade on each petiole
Each small blade on a compound leaf is
referred to as a leaflet
Sessile Leaves
Sessile leaves lack
petioles
Sessile Leaves
Grasses and certain other monocots have
sessile leaves that attach to the stem by way of
a sheath that seems to wrap around the stem
Leaf Mosaic
Alternate
Opposite
Whored
Leaf mosaic: the arrangement
of leaves on a stem
Leaf Mosaic
Alternate Mosaic: leaves alternate from
opposite sides of the stem (one petiole per
node)
Leaf Mosaic
Opposite Mosaic: two leaves grow from the
same point on the stem (two petioles per
node)
Leaf Mosaic
Whorled Mosaic: three or more leaves
grow from a single point on a stem (3 or
more petioles per node)
Leaf Mosaic
Leaf Shapes
Linear
Lobed
Circular
Cordate
Deltoid
Linear Leaf Shape
long and narrow
Lobed
Leaf Shape
Cordate Leaf Shape
kidney or heart-shaped
Deltoid Leaf Shape
deltoid-shaped
Circular Leaf Shape
Leaf Margins
Entire
Serrate
Undulate
Dentate
Entire Leaf Margin
smooth margin with no teeth
Serrate Leaf Margin
toothed margins
Undulate Leaf Margin
wavy margins
Dentate Leaf Margin
teeth point out