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Woody Structure (Anomalous Forms of Growth (Unequal Activity of the…
Woody Structure
Anomalous Forms of Growth
Anomalous Secondary Growth
roots of sweet potoatoes
storage parenchyma increased
numerous vascular cambia arise
around individual vessels
large
hundreds of cambia at various ages
irregular matrix of parenchyma
few sieve tubes
some vessels
Included Phloems
new vascular cambium arises
located between two bands of xylem
protection from insect
Unequal Activity of the Vascular Cambium
2 sectors of cambium very active
2 sectors almost completely inactive
stem grows outward in two directions
remains thin in the other two thin flat woody ribbon
flexibility
Secondary Growth in Monocots
some become tree-like and "woody"
Joshua trees
secondary vascular bundles
develop into fibers
thick secondary walls
dragon trees
palms
Unusual Primary Growth
palm trees
all primary tissue
vascular bundles
primary phloem
primary xylem
derived from shoot apical meristem
trunk does not grow radially
vascular cambium never develops
true wood does not occur
hard and "woody"
vascular bundle
1 more item...
secondary phloem does not occur
ground tissue
do not branch
trunks do not taper at tips
Hardwood sapwood
heartwood
almost always darker in color
one annual ring converted to heartwood each year
center of log
dryer and more fragrant
different regions because water columns break
tension
tylosis
bubbles of protoplasm
forms plug in vessels
wind
wood-boring insects
freezing
sapwood
outer region
lighter in color
moister
new layer formed each year
Reaction wood
response to stress
tension wood
eccentic
wider on top of the branch
prevent drooping
Vascular Cambium
only two types of cells
Ray Initials
short & cuboidal
produce short cells
storage parenchyma
albuminous cells
meristem that produce secondary plant body continue to divide instead of maturing
interfascicular cambium
fascicular cambium
Fusiform Initials
long tapered cells
periclinal wall
produce elongated cells of wood
xylem
tracheids
vessel elements
fibers
phloem
fibers
members companion cells
sieve tube
sieve cells
anticlinal wall
Secondary Xylem
Growth Rings vascular cambium quiescent during times of stress
early wood/ spring wood
first wood formed
wide vessels/wide tracheids
Late wood/ summer wood
ring growth
Spring and summer wood combined
diffuse porous
vessels form throughout growing season
ring porous
vessels restricted mainly to early wood
Types of Wood Cells all cells interior of vascular cambium=wood
xylem no new ones
axial system derived from fusiform initials
all cell types of primary
develops from ray
initials usually simple containing only parenchyma rays
store carbohydrates
store nutrients
Rays
uniseriate
biseriate
upright cells
multiseriate
procumbent cells
Arrangement of Cambial Cells
regular horizontal rows
storied cambium
without horizontal pattern
nonstoried cambium
Secondary Growth in Roots
roots of conifers
woody angiosperms
vascular cambium arises
ray initials
fusiform initials
wood produced in root
not identical to that of stems
Fusiform Initials
long tapered cells
periclinal wall
produce elongated cells of wood
xylem
tracheids
vessel elements
fibers
phloem
fibers
members companion cells
sieve tube
sieve cells
anticlinal wall
Fusiform Initials
long tapered cells
periclinal wall
produce elongated cells of wood
xylem
tracheids
vessel elements
fibers
phloem
fibers
members companion cells
sieve tube
sieve cells
anticlinal wall
Outer Bark
Cork and the Cork cambium
secondary phloem
cork cambium/phellogen
phelloderm
layer of parenchyma
outer cell differentiates into cork cell/phellem cel
inner bark
outer bark
after division inner cell remains cork cambium
periderm
cells are cuboidal
Lenticels and Oxygen Diffusion
lenticels
lenticels permits oxygen to penetrate bark
Iniitiation of Cork Cambia
variable
first cork cambium
depending on species can arise
region is several years old
epidermises more than 40 years old reported
before twig or root is even 1 year old
Secondary Phloem
formed from vascular cambium
axial system
conduction up/down stem/root
fibers
sieve tube member
conduct for less than 1 year
nonconducting parenchyma
companion cells
radial system
ray initial
phloem ray
only parenchyma cells
storage
Radical System
