structural organization of vascular plantsclasspages.warnerpacific.edu/bdupriest/bio 102/lecture 10...
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STRUCTURAL ORGANIZATION OF
VASCULAR PLANTS
The vascular plant body
plan
Root system
Shoot system
Stems
Leaves
Flowers
2
PLANT TISSUES
Tissue = collection of similar cells that
perform a common specialized function
Ground tissue
Bulk of the plant body
Vascular tissue
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
Ground, vascular, dermal
5
Tissue Development
Development of meristems
Ground meristem
Ground tissue
Procambium
Vascular tissue
Protoderm
Epidermis
6
Lateral Meristems
Periphery of shoots and roots
Growth in width (secondary growth)
Woody plants…
Vascular cambium
Produces secondary vascular tissue
Cork cambium
Produces bark
7
Ground Tissue
Tissues forming bulk of plant body
Simple tissues
1 type of cell
3 categories of ground tissue
8
Ground Tissue
Parenchyma
Soft moist tissues
Roots, stems, leaves,
flowers, fruits
Function
Photosynthesis, food
storage, water storage
9
Ground Tissue
Collenchyma
Function
Flexible support
Elongated cells layered with
pectin
Holds cellulose fibers
Maintains pliability
10
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 11
Vascular Tissue
Conducting tissues
Xylem
Transport of water & dissolved minerals
Phloem
Transport of sugars and other solutes
12
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
Tapered / overlap
Vessel members
End-end
Xylem
13
Phloem
Transport of sugars and other
solutes
2 types of elements
Sieve tube members
Sieve plate
Pores (large) between cells
Companion cells
Assist in sugar loading
Sieve cells
No companion cells
Gymnosperms & seedless
vascular plants 14
Dermal Tissue
Epidermis
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 15
Shoot System
Leaves Structure
Node
Petiole / sheath
Blade
Forms
Simple
Undivided
May be lobed
Compound
Blades divided into leaflets
On same plane 22
Root Structure
Vascularization
Dicots
Vascular cylinder at core of root
Surrounded by cortex (parenchyma)
27
Root Structure
Vascularization
Dicots
Monocots
Vascular cylinders in ring
Divide ground tissue
Pith
Cortex
29
Growth in width
Occurs in woody plants over multiple
seasons
Due to cell proliferation at lateral meristems
Secondary Growth
31
Wood & Bark
Wood
Accumulated secondary
xylem
Heartwood
No longer transporting
water
Waste storage: resins
and gums
Darken, strengthen
heartwood
Sapwood
Actively transporting water
34
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)
37
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