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Structure of Woody Plants (Secondary Growth in Roots (Roots (Do not store…
Structure of Woody Plants
Vascular Cambium
Initiation of the Vascular Cambium
Interfascicular cambium
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Fascicular cambium
Young cells
Bundle cells
Attached to Fascicular cambium
Young cells
Vascular cambium
Ray cells
Produce secondary plant body
Fusiform cels
Fusiform Initials
Thin primary walls
Periclinal wall
Increase cambial cells
Perpendicular to cambium
Axial phloem
Long tapered cells
Axial xylem
Arrangement of Cambial Cells
Non-storied cambium
Storied cambium
Ray Initials
Short
Store parenchyma
Undergo periclinal cell division
Xylem
Phloem
Secondary Xylem
Heartwood and Sapwood
Sapwood
Holds moisture
New layer yearly
Light
Heartwood
One ring is converted annually
Dark wood
Gets wider with age
Growth Rings
Annual rings
Late Wood
Summer wood
Lower portion vessels
Early wood
Porous
Spring wood
Higher portion vessels
Types of Wood Cells
Radial system
Ray parenchyma present
Formed from ray initials
Hardwood
Basal angiosperms
Eudicots
Have large amounts of fiber
Durable
Strong
Axial system
Conduction of water
No vessels (Conifers)
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Fibers rarely present (Conifers)
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Parenchyma rarely present (Conifers)
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Formed from fusiform initials
All present in Eudicots
Softwood
Can be harder than hardwood
Little to no fiber
Reaction Wood
Walls rich in cellulose
Growth rings wider at top
No lignin
Secondary Phloem
Formed in vascular cambium
Axial system
Companion cells present
Up and down growth
Fibers present
Sieve tubes present
Radial system
Only parenchyma cells present
Outer Bark
Lenticels and Oxygen Diffusion
No H2O absorption
Keeps pathogens out
Holds H2O
Initiation of Cork Cambia
Delayed bark formation
Forms in a year
Cork and the Cork Cambium
Cork cell (outer cell)
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Mature parenchyma layer (phelloderm)
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Cork cambium or phellogen
Periderm
Secondary Growth in Roots
Roots
Do not store H2O
Small rays
Sclerenchyma present
Sapwood
Perennial roots
Form bark
Cork arises in pericycle
Heartwood
Vascular cambium
Anomalous Forms of Growth
Anomalous Secondary Growth
Included phloem
Unequal activity of vascular cambium
Roots of Sweet Potatoes
Irregular matrix of parenchyma
Increase storage
Secondary tissue
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Secondary growth in monocots
Unusual Primary Growth
Palm Trees
Vascular cambium does not develop
Do not taper
Do not branch
Palm trunk
Primary xylem and phloem only
Do not grow rapidly
