STRUCTURAL
ORGANIZATION OF
VASCULAR PLANTS
STRUCTURAL ORGANIZATION OF
VASCULAR PLANTS

2
The vascular plant body
plan

Root system

Shoot system

Stems

Leaves

Flowers
PLANT TISSUES

Tissue = collection of similar cells that
perform a common specialized function

Ground tissue


Vascular tissue


Bulk of the plant body
Conduct water (xylem) and nutrients
(phloem)
Dermal tissue

Cover plant outer surfaces
3
Meristems

“Stem cells” that give rise to other plant
tissues and direct plant growth

Apical meristems

Lateral meristems
4
Apical Meristems



Tips of shoots and roots
Growth in length & height
(primary growth)
Give rise to other tissue layers

5
Ground, vascular, dermal
Tissue Development

Development of meristems

Ground meristem


Procambium


Vascular tissue
Protoderm

6
Ground tissue
Epidermis
Lateral Meristems

Periphery of shoots and roots

Growth in width (secondary growth)

Woody plants…

Vascular cambium


Cork cambium

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Produces secondary vascular tissue
Produces bark
Ground Tissue

Tissues forming bulk of plant body

Simple tissues

1 type of cell

3 categories of ground tissue
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Ground Tissue

Parenchyma

Soft moist tissues


Roots, stems, leaves,
flowers, fruits
Function

Photosynthesis, food
storage, water storage
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Ground Tissue

Collenchyma

Function


Flexible support
Elongated cells layered with
pectin

Holds cellulose fibers

Maintains pliability
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Ground Tissue

Sclerenchyma



Function

Strength, protection, support

Lines water conducting cells
Thick cell walls fortified with
lignin
Fibers or sclereids

Fibers support vascular
system


E.g., woven rope (Agave)
Sclereids: e.g., peach stones,
pear grit, coconut shell
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Vascular Tissue

Conducting tissues

Xylem


Transport of water & dissolved minerals
Phloem

Transport of sugars and other solutes
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Xylem

Transports water & dissolved minerals

Form continuous “pipelines” from roots to leaves

H2O diffuses through pores in walls

Mature cells die: provide support

2 types of elements

Tracheids


Vessel members

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Tapered / overlap
End-end
Phloem


Transport of sugars and other
solutes
2 types of elements

Sieve tube members

Sieve plate


Companion cells


Assist in sugar loading
Sieve cells

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Pores (large) between cells

No companion cells
Gymnosperms & seedless
vascular plants
Dermal Tissue

Epidermis



15
Provides protective outer covering over plant
surfaces
Specialized structures
 Cuticle
 Waxy outer covering
 Stomata
 Pores (stoma)
 Trichomes
 Root hairs
Replaced with secondary
growth (bark) in woody
plants
Dermal Tissue

Carniverous plants
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SHOOT SYSTEM

Stems

Dicots

Vascular bundles

Arranged in ring

Large
17
Dicot Stem
18
Vascular Bundle
19
Shoot System

Stems

Dicots

Monocots

Vascular bundles

Distributed throughout

Smaller
20
Dicot
Monocot Stem
21
Shoot System

Leaves


22
Structure
 Node
 Petiole / sheath
 Blade
Forms
 Simple
 Undivided
 May be lobed
 Compound
 Blades divided
into leaflets
 On same plane
Leaf Structure
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ROOT SYSTEM

Root structure

Primary root

Lateral roots

Root hairs
24
Root Structure

Types of roots

Tap root

Fibrous root
25
Fibrous Roots & Competition
26
Root Structure

Vascularization

Dicots

Vascular cylinder at core of root

Surrounded by cortex (parenchyma)
27
Dicot Root
28
Root Structure

Vascularization

Dicots

Monocots

Vascular cylinders in ring

Divide ground tissue

Pith

Cortex
29
Monocot Root
Dicot
30
Secondary Growth



Growth in width
Occurs in woody plants over multiple
seasons
Due to cell proliferation at lateral meristems
31
Secondary Growth
32
Secondary Growth
 secondary_growth
33
Wood & Bark

Wood


Accumulated secondary
xylem
Heartwood




No longer transporting
water
Waste storage: resins
and gums
Darken, strengthen
heartwood
Sapwood

Actively transporting water
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Wood & Bark

35
Bark

Cork

Cork cambium

Secondary phloem
Wood & Bark

Wood

Growth rings


Reflect seasonal
activity
Temperate regions
 1 ring per year
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Growth Rings

Spring xylem (early wood)

Lighter / wider

Larger diameter xylem


Optimum growing season
(light, water, temp)
Summer xylem (late wood)

Darker / narrower

Smaller diameter xylem

Slower growth (heat/cold,
less water)
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Hardwoods vs. Softwoods

Hardwood

E.g., oak, maple, cherry

Higher number of vessel members in xylem


Reinforced with collenchyma / sclerenchyma
fibers
Softwood

E.g., pine, fir, hemlock



Gymnosperms (conifers)
Xylem = tracheids (no vessel
members)
Lack supportive ground tissue
fibers
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