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Flowering Plants
ANGIOSPERMS
Angiosperm Diversity
• The two main groups of angiosperms are
monocots (one cotyledon) and dicots (two
cotyledons)
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Monocots
• More than one-quarter of angiosperm species
are monocots
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Fig. 30-13e
Orchid
Fig. 30-13e1
Pygmy date palm (Phoenix roebelenii)
Fig. 30-13f
Fig. 30-13g
Barley
Anther
Stigma
Ovary
Filament
Dicots
• More than two-thirds of angiosperm species
are eudicots
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Fig. 30-13h
California poppy
Fig. 30-13i
Pyrenean oak
Fig. 30-13j
Dog rose
Fig. 30-13k
Snow pea
Fig. 30-13l
Zucchini flowers
Fig. 30-13n
Monocot
Characteristics
Eudicot
Characteristics
Embryos
Two cotyledons
One cotyledon
Leaf
venation
Veins usually
parallel
Veins usually
netlike
Stems
Vascular tissue
scattered
Vascular tissue
usually arranged
in ring
Fig. 30-13o
Monocot
Characteristics
Eudicot
Characteristics
Roots
Taproot (main root)
usually present
Root system
usually fibrous
(no main root)
Pollen
Pollen grain with
one opening
Pollen grain with
three openings
Flowers
Floral organs
usually in
multiples of three
Floral organs usually
in multiples of
four or five
• Three basic organs evolved: roots, stems, and
leaves
• They are organized into a root system and a
shoot system
• Roots rely on sugar produced by
photosynthesis in the shoot system, and shoots
rely on water and minerals absorbed by the
root system
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Fig. 35-2
Reproductive shoot (flower)
Apical bud
Node
Internode
Apical
bud
Vegetative
shoot
Leaf
Shoot
system
Blade
Petiole
Axillary
bud
Stem
Taproot
Lateral
branch
roots
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Root
system
Roots
• Roots are multicellular organs with important
functions:
– Anchoring the plant
– Absorbing minerals and water
– Storing organic nutrients
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 35-14a1
Epidermis
Key
to labels
Cortex
Dermal
Endodermis
Ground
Vascular
Pericycle
Stele
Xylem
100 µm
Phloem
(a) Root with xylem and phloem in the center
(typical of eudicots)
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Fig. 35-14
Epidermis
Cortex
Endodermis
Pericycle
Core of
parenchyma
cells
Xylem
100 µm
Phloem
100 µm
(a) Root with xylem and phloem in the center
(typical of eudicots)
(b) Root with parenchyma in the center (typical of
monocots)
Endodermis
Pericycle
Key
to labels
Dermal
Ground
Vascular
Xylem
Phloem
50 µm
Stems
• A stem is an organ consisting of
– An alternating system of nodes, the points at
which leaves are attached
– Internodes, the stem segments between
nodes
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Fig. 35-17
Phloem
Xylem
Sclerenchyma
(fiber cells)
Ground
tissue
Ground tissue
connecting
pith to cortex
Pith
Epidermis
Key
to labels
Cortex
Epidermis
Vascular
bundle
Dermal
Vascular
bundles
Ground
1 mm
(a) Cross section of stem with vascular bundles forming
a ring (typical of eudicots)
Vascular
1 mm
(b) Cross section of stem with scattered vascular bundles
(typical of monocots)
Fig. 35-17a
Phloem
Xylem
Sclerenchyma
(fiber cells)
Ground tissue
connecting
pith to cortex
Pith
Key
to labels
Cortex
Epidermis
Vascular
bundle
Dermal
Ground
1 mm
(a) Cross section of stem with vascular bundles forming
a ring (typical of eudicots)
Vascular
Fig. 35-17b
Ground
tissue
Epidermis
Key
to labels
Dermal
Vascular
bundles
Ground
Vascular
1 mm
(b) Cross section of stem with scattered vascular bundles
(typical of monocots)
In most monocot stems, the vascular bundles are
scattered throughout the ground tissue, rather
than forming a ring
Leaves
• The leaf is the main photosynthetic organ of
most vascular plants
• Leaves generally consist of a flattened blade
and a stalk called the petiole, which joins the
leaf to a node of the stem
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• Monocots and dicots differ in the arrangement
of veins, the vascular tissue of leaves
– Most monocots have parallel veins
– Most dicots have branching veins
• In classifying angiosperms, taxonomists may
use leaf morphology as a criterion
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Fig. 35-6
(a) Simple leaf
Petiole
Axillary bud
Leaflet
(b) Compound
leaf
Petiole
Axillary bud
(c) Doubly
compound
leaf
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Leaflet
Petiole
Axillary bud
Fig. 35-6a
(a) Simple leaf
Petiole
Axillary bud
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Fig. 35-6b
Leaflet
(b) Compound
leaf
Petiole
Axillary bud
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Venation
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Monocot leave
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Tissue Organization of Leaves
• The epidermis in leaves is interrupted by
stomata, which allow CO2 exchange between
the air and the photosynthetic cells in a leaf
• Each stomatal pore is flanked by two guard
cells, which regulate its opening and closing
• The ground tissue in a leaf, called mesophyll,
is sandwiched between the upper and lower
epidermis
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• Below the palisade mesophyll in the upper part
of the leaf is loosely arranged spongy
mesophyll, where gas exchange occurs
• The vascular tissue of each leaf is continuous
with the vascular tissue of the stem
• Veins are the leaf’s vascular bundles and
function as the leaf’s skeleton
• Each vein in a leaf is enclosed by a protective
bundle sheath
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 35-18
Guard
cells
Key
to labels
Dermal
Ground
Cuticle
Vascular
50 µm
Stomatal
pore
Epidermal
cell
Sclerenchyma
fibers
Stoma
(b) Surface view of a spiderwort
(Tradescantia) leaf (LM)
Upper
epidermis
Palisade
mesophyll
100 µm
Spongy
mesophyll
Bundlesheath
cell
Lower
epidermis
Cuticle
Xylem
Vein
Phloem
(a) Cutaway drawing of leaf tissues
Guard
cells
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Vein
Air spaces Guard cells
(c) Cross section of a lilac
(Syringa)) leaf (LM)
Concept 35.4: Secondary growth adds girth to
stems and roots in woody plants
• Secondary growth occurs in stems and roots of
woody plants but rarely in leaves
• The secondary plant body consists of the
tissues produced by the vascular cambium and
cork cambium
• Secondary growth is characteristic of
gymnosperms and many eudicots, but not
monocots
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Fig. 35-19
(a) Primary and secondary growth
in a two-year-old stem
Epidermis
Cortex
Primary
phloem
Pith
Primary xylem
Epidermis
Vascular cambium
Primary phloem Cortex
Vascular
cambium
Primary
xylem
Pith
Vascular
ray
Primary
xylem
Secondary xylem
Vascular cambium
Secondary phloem
Primary phloem
First cork cambium
Cork
Periderm
(mainly cork
cambia
and cork)
Secondary phloem
Vascular cambium
Late wood
Secondary xylem
Early wood
Primary
phloem
Vascular
cambium
Secondary
xylem
Primary
xylem
Cork
cambium Periderm
Cork
Secondary
Xylem (two
years of
production)
Vascular cambium
Secondary phloem
Most recent
cork cambium
0.5 mm
Secondary
phloem
Bark
Bark
Cork
Layers of
periderm
Pith
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0.5 mm
Vascular ray Growth ring
(b) Cross section of a three-yearold Tilia (linden) stem (LM)
• The vascular tissue system carries out longdistance transport of materials between roots
and shoots
• The two vascular tissues are xylem and
phloem
• Xylem conveys water and dissolved minerals
upward from roots into the shoots
• Phloem transports organic nutrients from
where they are made to where they are needed
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• The vascular tissue of a stem or root is
collectively called the stele
• In angiosperms the stele of the root is a solid
central vascular cylinder
• The stele of stems and leaves is divided into
vascular bundles, strands of xylem and phloem
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• Annuals complete their life cycle in a year or
less
• Biennials require two growing seasons
• Perennials live for many years
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Assignments
1. Exclude e
2. Exclude c
3. All but we are using Coleus stems
4. Exclude b and j
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