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Structure of Woody Plants (Concepts (Secondary Growth (Eudicots (Present…
Structure of Woody Plants
Concepts
Bark
Makes plant wider
Greater capacity to move water and minerals upward
Greater capacity to move carbs downward
Greater Photosynthesis capacity
Secondary Tissues
Secondary Xylem
Woody
Trees
Firs
Pine
Chestnut
Sycamore
Shrubs
Oleanders
Azaleas
Roses
Abundant
Secondary Phloem and cork
Bark
Primary Tissues
Growth by means of apical meristem
Derived sets of tissues
Leaves
Vascular bundles
Cortex
Epidermis
Pith
Primary Plant body
Secondary Growth
Basal Angiosperms
Present in many species
Many other species are herbs
Eudicots
Present in many species
Many other species are herbs
Similar to Basal Angiosperms
Gymnosperms
Present in All species
Modern Ferns
Absent in all species
Monocots
Ordinary type is absent in all
Some have anomalous secondary growth
Secondary Xylem
Growth Rings
Late Wood
Summer wood
Lower proportion of vessels
Annual Ring
One years growth
Also known as growth rings
Early Wood
First Wood formed
Also called spring wood
Must have high proportion of wide vessels
Diffuse Porous
Vessels located throughout rings
Yellow birch
Aspen
Sugar maple
american holly
Ring Porous
Vessels restricted mainly to early wood
Red Oak
Sassafras
Honey Locust
HeartWood and SapWood
Sapwood
Lighter wood
Moister region
Heart Wood
Dark wood
Drier and more fragrant
Types of Wood Cells
Axial System
Derived from fusiform initials
Tracheids
Vessels
Fibers
Parenchyma
Radial System
Derived from ray initials
Ray Parenchyma
Procumbent cells
Upright cells
Ray Tracheids
Wood
Fibers
Sclereids
Vessel Elements
Parenchyma
Tracheids
Hardwoods
Contain large amounts of fibers
Wood of all basal angiosperms and eudicot
Softwoods
Few or no fibers
Softer consistency
Reaction Wood
Branches are no vertical
Have lateral stress
Angiosperms
Known as tension wood
Upper side of the branch
Conifers
Underside of branch
Known as compression wood
Secondary Phloem
Formed from vascular cambium
Axial System
Conduction up/down the stem or root
Contains __ in angiosperms
Sieve tube members
companion cells
Contains ___ in conifers
Sieve cells
contains a Radial System
#
Size, shape, and number of phloem rays
Produced by ray initials
Similar to xylem rays
Secondary Growth in Roots
Roots and vascular cambium contain
Ray initials
Fusiform Initials
Perennial roots
Form bark
Occurs in woody and conifer angiosperms
Lenticels can occur
Anomalous Forms of Growth
Anomalous Secondary Growth
Unequal Activity of Vascular Cambium
Very adaptive
Produced 4 sectors of cambium
2 sectors are almost completely inactive
2 sectors are very active
Remains flexible
Included Phloem
Located between 2 bands of xylem
No longer cambium
Protects Phloem from insects
Secondary Growth in Monocots
Parenchyma cells undergo division
Produce narrow cells
Differentiate into secondary vascular bundles
Vascular cambium arise outside bundles
Conducting cells are absent
Roots of sweet potatoes
Storage parenchyma is increased
Numerous vascular cambia arise
Larger sweet potatoes
May contain hundreds of cambia
Unusual Primary Growth
Establish growth
Occurs in monocots
Increased in size of width
Form of primary growth
Shoots and roots can become longer
Vascular Cambium
Fusiform Initials
#
Long, tapered cells
Periclinal wall
Longitudinal cell division forms
Produces two elongate cells
Secondary Xylem
Outer daughter cell remains cambium cell
Inner cell develops into secondary xylem
Secondary Phloem
Outer matures into secondary phloem
Inner continues as cambium cell
Anticlinal Walls
Vascular cambium divide longitudinally
Perpendicular to cambium surface
Ray Initials
#
Short and cuboidal
Similar to fusiform initials
Undergo Periclinal cell division
Produce short cells
Storage in parenchyma
Gymnosperms
Albuminous cells
Initiation of the Vascular Cambium
Produces secondary plant body
Fascicular Cambium
Continue to divide instead of mature
"Fascicle" means bundle
Never undergo cell cycle arrest
Interfascicular Cambium
Mature parenchyma cells between vascular bundles
Come out of cell cycle arrest
Resume mitosis
Connects each side with Fascicular cambia
Arrangement of Cambial Cells
Ray initials
Grouped together in short vertical rows
One, Two, or many cells wide
Fusiform initials
Grouped together in horizontal rows
Storied cambium
irregular, w/o horizontal rows
Nonstoried cambium
Outer Bark
Lenticels and Oxygen Diffusion
Lenticels
New cork cambium arises interior to this one
Outer and inner are aligned
Permits oxygen
To penetrate across all layers of bark
Aerenchymatous cork
Initiation of Cork Cambia
Different ages of bark have different characters
Timing is variable
Cork and Cork Cambium
Phelloderm
Produced by cork cambium
Mature layer of parenchyma
Periderm
Corkcambium, cork cells, and phelloderm
Maturing cork cells increase in volume
Thin primary walls
Encrusted in suberin
Cork Cell
Also known as phellem cell
Outer layer of cork cambium
Outer Bark
All tissues outside innermost cork cambium
Cork Cambium
Also known as phellogen
Cuboidal in shape
Form of secondary phloem
Inner Bark
All secondary phloem
Between vascular cambium and innermost cork cambium
Radial system contains ray initials
Secondary Phloem and Secondary Xylem both contain radial and axial systems
Fusiform Initials contain secondary xylem
