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Plant Tissues and the
Multicellular Plant Body
Chapter 5
LEARNING OBJECTIVE 1
•
Discuss the plant body, including the
root system and shoot system
The Plant Body 1
•
Root system
•
•
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generally underground
obtains water and dissolved minerals for plant
usually anchors the plant firmly in place
The Plant Body 2
•
Shoot system
•
•
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generally aerial
obtains sunlight and carbon dioxide for plant
Shoot system consists of
•
•
a vertical stem bearing leaves (main organs of
photosynthesis)
flowers and fruits (reproductive structures)
The Plant Body 3
•
Buds (undeveloped embryonic shoots)
develop on stems
•
Although separate organs (roots, stems,
and leaves) exist in the plant, many
tissues are integrated throughout the
plant body, providing continuity from organ
to organ
The Plant Body
Developing fruit
Nodes (areas of leaf and
axillary bud attachment)
Flower
Shoot
system
Axillary bud
Internode (area between
adjacent nodes)
Petiole Blade
Stem
Leaf
Rosette of
basal leaves
Root
system
Taproot
Branch roots
Fig. 5-1, p. 92
Developing fruit
Nodes (areas of leaf and
axillary bud attachment)
Flower
Shoot
system
Axillary bud
Internode (area between
adjacent nodes)
Petiole Blade
Stem
Leaf
Rosette of
basal leaves
Root
system
Taproot
Branch roots
Stepped Art
Fig. 5-1, p. 92
KEY TERMS
•
GROUND TISSUE SYSTEM
•
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VASCULAR TISSUE SYSTEM
•
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All tissues of the plant body other than
vascular tissues and dermal tissues
Tissue system that conducts materials
throughout the plant body
DERMAL TISSUE SYSTEM
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Tissue system that provides an outer covering
for the plant body
3 Tissue Systems in Plant Body
Dermal tissue system
Vascular tissue system
Ground tissue system
(a) Leaf
Dermal tissue system
Vascular tissue system
Ground tissue system
(b) Stem
Dermal tissue system
Vascular tissue system
Ground tissue system
(c) Root
Fig. 5-2, p. 94
LEARNING OBJECTIVE 2
•
Describe the ground tissue system
(parenchyma tissue, collenchyma
tissue, and sclerenchyma tissue) of
plants
KEY TERMS
•
PARENCHYMA CELL
•
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COLLENCHYMA CELL
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Relatively unspecialized plant cell; thin walled,
may contain chlorophyll, loosely packed
Living plant cell with moderately but unevenly
thickened primary walls
SCLERENCHYMA CELL
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Plant cell with extremely thick walls; provides
strength and support to plant body
Ground Tissue System 1
•
Parenchyma tissue
•
•
Composed of living parenchyma cells with
thin primary cell walls
Functions include photosynthesis, storage,
and secretion
Parenchyma Cells
Parenchyma Cells
Vacuole
Nucleus
Onion
(a) Parenchyma cells from an epidermal peel
of red onion (Allium cepa). The large vacuole
contains pigmented material and occupies
most of the cell. The nucleus and cytoplasmic
strands are positioned under and on top of
the vacuole, between it and the plasma
membrane.
Fig. 5-3a, p. 96
Chloroplasts
Elodea
(b) Some parenchyma cells contain chloroplasts,
and their primary function is photosynthesis.
These parenchyma cells are from a waterweed
(Elodea) leaf.
Fig. 5-3b, p. 96
Starch
grains
Buttercup
(c) Parenchyma cells often function in storage.
These parenchyma cells are from a buttercup
(Ranunculus) root. Note the starch grains filling
the cells.
Fig. 5-3c, p. 96
Ground Tissue System 2
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Collenchyma tissue
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Composed of collenchyma cells with
unevenly thickened primary cell walls
Provides flexible structural support
Collenchyma Cells
Thick cell walls at corners
of 4 cells
Cell's
interior
Water lily
Fig. 5-4, p. 97
Ground Tissue System 3
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Sclerenchyma tissue
•
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Composed of sclerenchyma cells with both
primary and secondary cell walls
Sclerenchyma cells are often dead at maturity,
but provide structural support
Sclerenchyma Cells
Cherry
Bamboo
Fiber cells
Parenchyma
cell
(a) Sclereids from a cherry (Prunus avium) stone. The
cell walls are extremely thick and hard, providing
structural support.
(b) Long, tapering fibers and shorter parenchyma
cells from a bamboo (Bambusa) stem. The stem
was treated with acid to separate the cells.
Fig. 5-5, p. 97
LEARNING OBJECTIVE 3
•
Outline the structure and function of
the vascular tissue system (xylem and
phloem) of plants
Vascular Tissue System
•
Conducts materials throughout the plant
body and provides strength and support
•
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Xylem
Phloem
KEY TERMS
•
XYLEM
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A complex vascular tissue that conducts water
and dissolved minerals throughout the plant
body
Actual conducting cells of xylem are
tracheids and vessel elements
Xylem
Pits
Tracheids
White pine tree
(a) Tracheids from a white pine (Pinus strobus) stem in longitudinal section (that is, cut
lengthwise). These cells, which occur in clumps, transport water and dissolved minerals.
Water passes readily from tracheid to tracheid through pits, thin places in the cell wall.
Fig. 5-6a, p. 98
Vessel elements
Pumpkin plant
(b) Vessel elements from a pumpkin (Cucurbita mixta) stem in longitudinal section. The
blue-stained regions are various patterns of the secondary walls in the vessel elements.
Perforation plates are not visible in this micrograph.
Fig. 5-6b, p. 98
Adjacent
perforation
plates
Southern
magnolia
(c) The end walls of vessel elements, called perforation plates, have large holes. Water
passes through the perforation plate from one vessel element to the next. Shown are
adjacent perforation plates from a southern magnolia (Magnolia grandiflora) stem; in this
species, the perforation plates are at an angle in longitudinal section.
Fig. 5-6c, p. 98
Pit Pairs
Pit Pairs
Pit Pairs
Pits
Middle lamella
Permeable
primary cell
wall pair
Impermeable
secondary
cell walls
Tracheid Simple
pit
Cell A
Primary
cell walls
Cell B
(a) A simple pit pair has an interruption in the secondary cell wall. The primary
cell wall in a simple pit pair is permeable to water.
Fig. 5-7a, p. 101
Primary
cell walls
Bordered
pit
Torus
Pit borders
Cell A
Cell B
Secondary
cell walls
(a) A simple pit pair has an interruption in the secondary cell
wall. The primary cell wall in a simple pit pair is permeable to
water.
Fig. 5-7b, p. 101
Water
Pressure
closes pit
Cell A
Water
H2O
Cell B
Cell A
Cell B
(c) (Left ) When water pressure is equal between the two
cells (A and B), the bordered pit is open, and water flow is
unrestricted. (Right ) When the pressure is greater in cell A
than in cell B, the torus, a thickening in the primary cell
walls, blocks the opening, restricting water movement
through the pit pair.
Fig. 5-7c, p. 101
KEY TERMS
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PHLOEM
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A complex vascular tissue that conducts food
(carbohydrate) throughout the plant body
Conducting cells of phloem are sieve-tube
elements assisted by companion cells
Phloem
Sievetube
elements
Cross
section
Squash leaves
Sieve
plate
Companion
cell
(a) Phloem tissue from a squash (Cucurbita) petiole in cross section. Note the
sieve plates, the end walls of the sieve-tube elements. Most sieve-tube elements
appear empty because they were sectioned in the middle of the cells rather than
at the end walls. The smaller cells are companion cells.
Fig. 5-8a, p. 102
Companion cell
Sieve-tube
element
Longitudinal
section
Squash leaves
Sieve plate
(b) Phloem tissue from a squash (Cucurbita) petiole in longitudinal section.
Fig. 5-8b, p. 102
LEARNING OBJECTIVE 4
•
Describe the dermal tissue system
(epidermis and periderm) of plants
Dermal Tissue System
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Outer protective covering of the plant body
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Epidermis
Periderm
KEY TERMS
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EPIDERMIS
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Outermost tissue layer, usually one cell thick
Covers the primary plant body (leaves, young
stems and roots)
Epidermis
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Epidermis covering aerial parts secretes a
wax layer (cuticle) that reduces water loss
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Gas is exchanged between interior of shoot
system and surrounding atmosphere
through stomata
Epidermis
Epidermal
cells
Guard cells
Stoma
Spiderwort
Fig. 5-9, p. 103
KEY TERMS
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PERIDERM
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Outermost layer of cells covering a woody
stem or root (the outer bark that replaces
epidermis when it is destroyed during
secondary growth)
Periderm
Exterior
environment
Remnants
of epidermis
Cork cells
Cork
cambium
Cork
parenchyma
Periderm
Geranium
Cortex
(interior of stem)
Fig. 5-10, p. 103
LEARNING OBJECTIVE 5
•
Discuss what is meant by growth in
plants and how it differs from growth in
animals
Growth in Plants
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Involves cell division, cell elongation, and
cell differentiation
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Plants grow only in specific areas
(meristems) composed of cells that do not
differentiate
Growth in Animals
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Location of growth differs between plants
and animals
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When a young animal grows, all parts of
its body grow, although not necessarily at
the same rate
LEARNING OBJECTIVE 6
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Distinguish between primary and
secondary growth
KEY TERMS
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PRIMARY GROWTH
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An increase in stem and root length due to the
activity of apical meristems at the tips of
roots and at the buds of stems
KEY TERMS
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APICAL MERISTEM
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An area of cell division at the tip of a stem or
root in a plant; produces primary tissues
BUD
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A dormant embryonic shoot that eventually
develops into an apical meristem
Root Tip
Area of cell
maturation
Root hairs
Area of cell
elongation
Protoderm
Ground meristem
Procambium
Area of cell division
Apical
meristem
Root cap
Fig. 5-11, p. 105
Stem Tip
Older
leaf
Leaf
primordia
Apical
meristem
Older
leaf
Trichome
Bud
primordium
Coleus
Fig. 5-12, p. 106
Stem Tip Development
Immature leaf
Stem apical
meristem
Area of cell
division
Procambium
Protoderm Procambium Ground meristem
Area of cell
elongation
Epidermis
Area of cell
maturation
Cortex Procambium Pith Primary xylem Primary phloem
Fig. 5-13, p. 106
KEY TERMS
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SECONDARY GROWTH
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An increase in a plant’s stem and root girth
due to the activity of lateral meristems (the
vascular cambium and cork cambium)
Secondary Growth
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Woody plants have secondary growth
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In addition to primary growth
Secondary growth is localized, typically as
long cylinders of active growth throughout
the lengths of older stems and roots
KEY TERMS
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LATERAL MERISTEM
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An area of cell division on the side of a
vascular plant; the two lateral meristems
(vascular cambium and cork cambium) give
rise to secondary tissues
Lateral Meristems and
Secondary Growth
Outer bark (periderm)
Inner bark (secondary phloem)
Bark
Wood
(secondary xylem)
Surface of vascular cambium
Fig. 5-14, p. 107
Animation: Tissue Systems of
a Tomato Plant
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TO PLAY
Animation: Root Organization
root_structure.swf
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TO PLAY
Animation: Shoot
Differentiation
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Transport in Plants: Animations
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http://plantandsoil.unl.edu/croptechnology
2005/pages/animationOut.cgi?anim_name
=RootUptake.swf
http://wps.aw.com/bc_nabors_botany_1/15
/4076/1043540.cw/nav_and_content/index
.html