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Ch. 8 Structure of Woody plants (Growth (Anomalous Forms in Growth…
Ch. 8 Structure of Woody plants
Growth
Anomalous Forms in Growth
Anomalous secondary growth
alternative cambia producing secondary bodies
differs from the common type
Secondary Growth in Monocots
secondary vascular bundles
narrow cells containing xylem and phloem
outermost cells develop into fibers
secondary ground tissue is formed
Included phloem
cells in oldest secondary phloem become reactivated
differentiates to new vascular cambium
vascular cambium arises
secondary phloem located between bands of xylem
Roots of Sweet Potatoes
increased storage parenchyma
numerous vascular cambia arise
Unequal activity of the Vascular Cambium
ex.
Bauhinia
2 sectors active, 2 inactive
capacity increases, flexibility decreases
stem grows outward in 2 directions
but remains thin in the other 2
Unusual Primary Growth
establishment growth
increase in width
addition of adventitious roots
occurs in other monocots with broad sterns
Concepts
Vascular Cambium
Initiation of the Vascular Cambium
vascular cambium
produces secondary plant body
never undergoes cell cycle arrest
divide instead of maturing
forming fascicular cambium
fascicular cambium
some cells resume mitosis
forming interfascicular cambium
interfascicular cambium
vascular cambium is complete cylinder
Fusiform Initials
long, tapered cells
percinal wall
producing 2 elongate cells
one continues to be fusiform initial
other differentiates to either
secondary xylem
secondary phloem
anticlinal walls
increases # of cambial cells
without this division
cambial cells would be stretched
too stretched to function
Ray Initials
short
more or less cuboidal
produce
elongate cells of wood & phloem
storage parenchyma
albuminous cells
Arrangement of Cambial Cells
ray initials
grouped in short/vertical rows
multiseriate
uniseriate
biseriate
fusiform initials
storied cambium
regular horizontal rows
redbud
persimmon
nonstoried cambium
irregular, no pattern
single vascular cambium
form of cylinder
Secondary Xylem
Types of Wood Cells
radial system
develops from ray initials
axial system
derived from fusiform initials
hardwood
wood of basal angiosperms/eudicots
softwood
softer consistency
few or no fibers
ex.
pines
redwoods
upright cells
have connection with axial cells
procumbent cells
no connection with axial cells
secondary xylem
AKA wood
wood may contain
tracheids
vessel elements
fibers
sclereids
parenchyma
ray tracheids
horizontal, rectangular cells
have
secondary walls
circular bordered pits
protoplasts
cells formed to interior of vascular cambium
AKA wood
Growth Rings
Annual Ring
late wood
AKA summer wood
lower proportion of vessels
stronger because increased # of leaves
early wood
high proportion of wide vessels, or tracheids
AKA spring wood
alternative arrangement
diffuse porous
vessels located throughout
ex.
Aspen
Sugar Maple
Yellow Birch
ring porous
vessels restricted
ex.
Red Oak
Sassafras
Honey Locust
Heartwood & Sapwood
Heartwood
dark wood
more fragnant
center of log
Sapwood
lighter wood
moister outer region
new layer formed each year
tylosis
plug
formed by protoplasm in the pits
Reaction Wood
known as tension wood
exert tension on branch
preventing from drooping
growth rings are eccentric
Outer Bark
Cork and Cork Cambium
periderm
cork cell
AKA phellem cell
outer cell
phelloderm
layer of parenchyma
cork cambium
AKA phellogen
offers temporary protection
Outer Bark
tissues outside innermost C.C.
Inner Bark
all secondary phloem
between vascular cambium & innermost C.C.
Secondary Phloem
formed from vascular cambium
has axial and radial system
axial secondary phloem
fibers are present
nonconducting parenchyma are present
phloem/xylem rays
both produced from same initial
