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Chapter 29: Plant Tissues
Shoots and Roots • Shoots (Leaves and Stem)
– Produce food by photosynthesis
– Carry out reproductive functions
• Roots
– Anchor the plant
– Penetrate the soil and absorb water and
dissolved minerals
Shoot Apical Meristem
primary
meristems
active
epidermis, ground
tissues, primary
vascular tissues
forming
epidermis, ground
tissues, primary
vascular tissues
forming
primary
meristems
active
Root Apical Meristem
Fig. 29-3a, p.494
Protoderm
Ground meristem
Procambium
epidermis
ground tissues
primary vascular tissues
The cellular descendants of apical meristems divide, grow, and differentiate. They
form three primary meristems, the activity of which lengthens shoots and roots:
Fig. 29-3a1, p.494
vascular cambium
cork cambium
Lateral Meristems
thickening
Fig. 29-3b, p.494
Angiosperm Body Plan
VASCULAR TISSUES
GROUND TISSUES
SHOOT SYSTEM
ROOT SYSTEM
EPIDERMIS
Ground tissue
system
Vascular tissue
system
Dermal tissue
system
Fig. 29-2, p.494
Monocots and Dicots:
Parallel veins Netlike veins
3 pores 1 pore
4 or 5
floral
parts
3 floral
parts
1 cotyledon 2 cotyledons
Vascular
bundles
dispersed
Vascular
bundles
in ring
Inside seeds, two
cotyledons seed
leaves of embryo
Usually four or
five floral parts
(or multiples of
four or five)
Leaf veins
usually in a
netlike array
Three pores or
furrows in the
pollen grain surface
Vascular bundles
organized as a ring
in ground tissue
Inside seeds, one
cotyledon seed leaf
of embryo
Usually three
floral parts (or
multiples of
threes)
Leaf veins usually
running parallel
with one another
One pre or furrow in
the pollen grain
surface
Vascular bundles
distributed throughout
ground tissue Fig. 29-4, p.495
Parenchyma: A Simple Tissue
• Most of a plant’s soft primary growth
• Pliable, thin walled, many sided cells
• Cells remain alive at maturity and retain
capacity to divide
• Mesophyll is a type that contains
chloroplasts
stem epidermis
simple and complex tissues inside the stem
parenchyma
vessel of
xylem phloem
fibers of
sclerenchyma
Fig. 29-6, p.496
Collenchyma: A Simple Tissue
• Specialized for support for primary tissues
• Makes stems strong but pliable
• Cells are elongated
• Walls thickened with pectin
• Alive at maturity
Collenchyma: A Simple Tissue
• Supports mature plant parts
• Protects many seeds
• Thick, lignified walls
• Dead at maturity
• Two types:
– Fibers: Long, tapered cells
– Sclereids: Stubbier cells
collenchyma parenchyma lignified secondary wall
Fig. 29-7, p.496
Complex Tissues
Composed of a mix of cell types
Xylem
Phloem
Epidermis
Xylem
Conducts water
and dissolved
minerals up the
shoot
Conducting cells
are dead and
hollow at maturity vessel
member tracheids
one
cell’s
wall
pit in
wall
sieve plate
of sieve
tube cell
companion
cell
a b c
Fig. 29-8, p.497
Phloem: A Complex Vascular Tissue
• Transports sugars
down the shoot
• Main conducting
cells are sieve-tube
members
• Companion cells
assist in the loading
of sugars
sieve plate
sieve-tube
member
companion
cell
Epidermis: A Complex Plant Tissue
• Covers and protects plant surfaces
• Secretes a waxy, waterproof cuticle
• In plants with secondary growth,
periderm replaces epidermis
leaf surface cuticle epidermal cell photosynthetic
cell
Fig. 29-9, p.497
Meristems
• Regions where cell divisions produce plant growth
• Apical meristems – Lengthen stems and roots
– Responsible for primary growth
• Lateral meristems – Increase width of stems
– Responsible for secondary growth
Apical Meristems
activity at
meristems
new cells
elongate
and start to
differentiate
into primary
tissues
activity at
meristems
new cells
elongate
and start to
differentiate
into primary
tissues
Root apical meristem
Shoot apical meristem
Fig. 29-10a1, p.498
immature leaf
shoot apical meristem
lateral bud forming
vascular tissues
pith
cortex
Fig. 29-10a2, p.498
immature leaf
shoot apical
meristem
descendant
meristems
(orange)
Fig. 29-10b, p.498
Lateral Meristems
• Increase girth of older roots and stems
• Cylindrical arrays of cells
vascular cambium cork
cambium
thickening
Figure 29.20.a
Page 504
immature leaf
shoot apical meristem descendant
meristems
(orange)
Stepped Art
Fig. 29-10b-d, p.498
primary phloem
primary xylem
pith
cortex
Internal Structure of a Dicot Stem
• Outermost layer is epidermis
• Cortex lies beneath epidermis
• Ring of vascular bundles
separates the cortex from the
pith
• The pith lies in the center of the
stem
Internal Structure of a Monocot
Stem
• The vascular bundles
are distributed
throughout the ground
tissue
• No division of ground
tissue into cortex and
pith
Figure 29.11.b
Page 499
cortex
epidermis
vascular
bundle
pith
vessel
in xylem
meristem
cell
sieve tube
in phloem
companion
cell in
phloem
Fig. 29-11a, p.499
Common Leaf Forms
petiole
blade
axillary
bud
node
blade
sheath
node
DICOT MONOCOT
Figure 29.12.a,b
Page 500
Adapted for Photosynthesis
• Leaves are usually thin
– High surface area-to-volume ratio
– Promotes diffusion of carbon dioxide in, oxygen
out
• Leaves are arranged to capture sunlight
– Are held perpendicular to rays of sun
– Arranged so they don’t shade one another
POPLAR
(Populus)
OAK
(Quercus)
MAPLE
(Acer)
leaflet
RED
BUCKEYE
(Aesculus)
BLACK
LOCUST
(Robina)
HONEY LOCUST
(Gleditsia)
Fig. 29-12c,d, p.500
Leaf Structure
UPPER
EPIDERMIS
PALISADE
MESOPHYLL
SPONGY
MESOPHYLL
LOWER
EPIDERMIS
one stoma
cuticle
O2 CO2
xylem
phloem
Figure 29.14.b
Page 501
leaf blade
leaf vein
stem
Leaf Vein
(one vascular
bundle) cuticle
Upper
Epidermis
Lower
Epidermis
Palisade
Mesophyll
Spongy
Mesophyll
50m
xylem
phloem
cuticle-coated cell
of lower epidermis
one stoma (opening
across epidermia)
Oxygen and
water vapor
diffuse out
of leaf at
stomata.
Carbon
dioxide in
outside air
enters leaf at
stomata.
Water, dissolved mineral ions from roots and stems move into leaf vein (blue arrow)
Photosynthetic
products (pink
arrow) enter
vein, will be
transported
throughout
plant body
Fig. 29-14, p.501
Leaf Veins: Vascular Bundles
• Xylem and phloem; often
strengthened with fibers
• In dicots, veins are netlike
• In monocots, they are parallel
Fig. 29-15a, p.501
Leaf Veins
Fig. 29-15b, p.501
Leaf Veins
Root Systems
Taproot system of
a California poppy
Fibrous root system
of a grass plant Figure 29.19
Page 503
Internal Structure of a Root
• Outermost layer is epidermis
• Root cortex is beneath the epidermis
• Endodermis, then pericycle surround the
vascular cylinder
• In some plants, there is a central pith
Root Structure
• Root cap covers tip
• Apical meristem produces
the cap
• Cell divisions at the apical
meristem cause the root to
lengthen
• Farther up, cells differentiate
and mature Figure
29.16.a
Page 502
primary xylem
primary phloem
epidermis
VASCULAR
CYLINDER
cortex
pith
Fig. 29-17, p.503
Fig. 29-18, p.503
Function of Endodermis
• Ring of cells surrounds vascular cylinder
• Cell walls are waterproof
• Water can only enter vascular cylinder by moving
through endodermal cells
• Allows plant to control inward flow
Root Hairs and Lateral Roots
• Both increase the surface area of
a root system
• Root hairs are tiny extensions of
epidermal cells
• Lateral roots arise from the
pericycle and must push through
the cortex and epidermis to reach
the soil
new
lateral
root
Fig. 29-19a, p.503
Fig. 29-19b, p.503
Secondary Growth
• Occurs in all gymnosperms, some
monocots, and many dicots
• A ring of vascular cambium produces
secondary xylem and phloem
• Wood is the accumulation of these
secondary tissues, especially xylem
Fig. 29-20, p.504
primary xylem
primary phloem
VASCULAR CAMBIUM
VASCULAR CAMBIUM
secondary xylem
secondary phloem
stem surface
Fig. 29-20b, p.504
Secondary Growth
Figure 29.20.c
Page 504
Ongoing cell divisions
enlarge the inner core of
secondary xylem and
displace vascular cambium
toward the stem
pericycle
procambium
cortex
primary phloem
epidermis
Fig. 29-22a, p.505
endodermis
primary xylem
Woody Roots
vascular cambium produced by pericycle
vascular cambium produced by procambium
secondary xylem
secondary phloem
vascular cambium
vascular ray
cortex, epidermis slough off
crushed primary phloem
pericycle derivatives
epidermis cortex
endodermis pericycle
primary xylem
primary phloem
procambium
Stepped Art
Fig. 29-22, p.505
Fig. 29-23, p.506
A Coast
Redwood
periderm (includes
cork cambium, cork,
new parenchyma)
secondary
phloem
BARK
vascular cambium
HEARTWOOD SAPWOOD
Fig. 29-24a, p.507
Annual Rings
• Concentric rings of secondary xylem
• Alternating bands of early and late wood
• Early wood
– Xylem cells with large diameter, thin walls
• Late wood
– Xylem cells with smaller diameter, thicker walls
Fig. 29-25a, p.507
1587–1589 1606–1612
Fig. 29-27c, p.509
Annual Rings Narrow annual rings mark severe drought
years