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Structure of Woody Plants (Vascular Cambium (Fusiform Initials (Anticlinal…
Structure of Woody Plants
Vascular Cambium
Fusiform Initials
Long, tapered cells.
Periclinal Wall
When a fusiform undergoes cell division with a wall parralel
Cambial cells produce narrow daughter cells
Anticlinal walls
Perpendicular to cambrium's surface
Occurs when vascular cells must divide longitudinally
Thin primary walls
Plastids are present as Protoplastids
Ray Initials
Similar to fusiform
Also undergo periclinal cell divisions
Short and cuboidal
Differences
Elongate fusiform cells produce elongate cells of wood
Initiation of the Vascular Cambium
Helps produce secondary plant body
Fascicular Cambrium
Cells in a position that don't undergo cell cycle arrest
Interfascicular Cambrium
Connects on each side with Fascicular Cambria
Formed by some mature parenchyma cells
Arrangement of Cambial Cells
Initials
Fusiform
Occurs in horizontal rows
Can occur in irregular patterns
Ray
Grouped in short vertical rows
Vascular Cambium
Never has large regions of either initial one way.
Secondary Xylem
Growth Rings
Early wood
Wood formed at beginning stages of life.Wide vessels.
Late wood
Wood produced after the cuticle has thickened, transpiration is less, and new vessels are functioning
Annual ring
Early wood and late wood put together when observed
Growth ring
Another term for the visible ring inside a tree's trunk, displaying how long a tree has lived.
Heartwood and Sapwood
Heartwood
Darker, drier wood.
Becomes wider with age
Sapwood
Lighter and moister outer region wood.
New layer formed each year
Thickness is rather constant
Types of Wood Cells
Axial System
Vessels
Present in Eudicots
Fibers
Present in Eudicots
Tracheids
Present in Conifers and Eudicots
Parenchyma
Rare in Conifers, present in Eudicots
Radial System
Ray Parenchyma
Present in both Conifers and Eudicots
Ray Tracheids
Present in Conifers
Reaction Wood
Helps support plant
Develops on upper side of branch in angiosperms
Growth rings are eccentric
Conifers form this on the underside of the branch
Outer Bark
Lenticels and Oxygen Diffusion
Impermeability of cork doesn't allow oxygen to pass easily.
Lenticels
Regions of aerenchymatous cork
Allows passage of O2
Initiation of Cork Cambria
Timing is quite variable
First bark on young stems usually differs from when bark is older.
Cork and Cambium
Also called Phellogen
Differs greatly from vascular cambium
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Cork cell
Phellem Cell
Results of differentiation. Outer layer.
Phelloderm occasionally produced
Periderm is the combination of Phelloderm, layers of cork, and the cambium
Anomalous Forms of Growth
Secondary Growth
Monocots
None have secondary growth like that in gymnosperms, angiosperms, etc.
Some become treelike
Can produce secondary vascular bundles
Unequal Activity of Vascular Cambrium
In some species, 2 sectors of cambium remain very active while 2 are almost inactive
Stem grows outward in 2 directions but remains dormant in other 2.
Flexibility, in Bauhina, generally remains the same
Roots of Sweet Potatoes
Stored parenchyma increased dramatically
Cambia acts normally, except parenchyma is produced mostly
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May contain hundreds of cambia at various ages
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Primary Growth
Palms
Major example of anomalous growth
Increase in width and addition of adventitious roots: establishment growth
At some point, the process stops.
Same type of growth occurs in monocots
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1 layer of cells, meristem, and vascular cambrium
