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Structure of Woody Plants (Secondary Growth (Primary issues (Vascular…
Structure of Woody Plants
Vascular Cambium
Initiation of Vascular Cambium
Fascicular cambium
Between metaxylem and metaphloem
Forms new xylem/phloem
Interfascicular cambium
Between vascular bundles
Forms new parenchyma
Arrangement of Cambial Cells
Ray Initials
Short vertical rows
Biseriate
Muiltiseriate
Uniseriate
Fusiform Initials
Storied cambium
Regular horizontal rows
Nonstoried cambium
Irregular patterns
Fusiform initials
Long, tapered cells
Perclinal division
Parallel to cambium
Produce elongate wood cells
Phloem
Xylem
Anticlinal division
Perpendicular to cambium
Produce more cambial cells
Ray Initials
Short & Cuboidal
Both cambia cells are cuboidal
Periclinal division
Produce short cells
Parenchyma cells
Albuminous cells in gymnosperms
Secondary Growth
Primary issues
Vascular Bundles
Pith
Cortex
Leaves
Epidermis
Secondary tissues
Wood
Bark
Advantages
Plant grows wider
Greater transport capacity
Increased photosynthetic capacity
Increased number of leaves/roots
Disadvantages
Bigger target for predators
Battles environment much longer
Metabolically expensive
Late reproduction
Location
Most basal angiosperms
Gymnosperms
Many eudicots
Secondary Xylem
Growth rings
Annual Ring
Late Wood
Summer Wood
Typically less vessels
Fibers
Early Wood
Spring Wood
Ring porous
Wide vessels or tracheids
Alternative arrangement
Vessels all growing season
Diffuse porous
Heartwood and sapwood
Heartwood
Dark
Center of tree
Becomes wider overtime
Sapwood
Lighter
Outer region of tree
Stays same thickness
Sapwood to heartwood
Vessels/tracheids die
Adjacent parenchyma form tylosis
Parenchyma dies
Arrangement
Division into axial/radial systems
Axial System
Develops from fusiform initials
Contains tracheary elements
Fibers
Axial xylem parenchyma
Radial System
Develops from ray initials
Rays
Upright Cells
Procumbent Cells
Reaction Wood
Tension wood
Upper side of branch
Compression Wood
Underside of branch
Counteracts stress of gravity
Secondary Phloem
Constitutes the inner bark
Axial System
Conduction Root/ Stem
Sieve cells
Companion cells
Sieve tube members
Fibers
Nonconducting parenchyma
Radial System
Phloem rays
Parenchyma cells
Outer Bark
Lenticels
Aerencymateous cork regions
Oxygen diffusion
Protrude outward
Initiation of cork cambia
Very variable
Many places to arise
Cortex
Primary phloem
Epidermis
Secondary phloem
Cork and Cork Cambium
Cork cambium
Phellogen
Cuboidal cells
Division and differentiation
Cork cells
Phellem cells
Phelloderm
Periderm
Phellem
Phelloderm
Phellogen
Tissue arrangement
Outer bark
Outside innermost cork cambium
Inner bark
Inside innermost cork cambium
Secondary Growth in Roots
Vascular cambium
Ray initials
Fusiform initials
Differences from stem wood
Water conduction by diffusion
Strengthened by wood fibers
No water storage
Small rays of sclerenchyma
Wood almost all parenchyma
Anomalous Forms of Growth
Secondary Growth
Included Phloem
Multiple xylem/phloem layers
Unequal Activity Vascular Cambium
Two cambium sectors active
Two cambium sectors inactive
Roots Sweet Potatoes
Multiple vascular cambia
Forms around individual vessel(s)
Secondary growth in monocots
Secondary vascular bundles
Unusual Primary Growth
Palm trees
Vascular bundles added
Establishment growth
