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Ch 8: Structure of Woody Plants (Vascular Cambium (Fusiform Initials (long…
Ch 8: Structure of Woody Plants
Secondary Growth in Roots
Vascular Cambium
Initiation of the Vascular Cambium
Vascular Cambium
Fascicular cambium
secondary plant body producer
inter fascicular bundle
Fusiform Initials
long, tapered cells
cells within cambium
ray initials
short and cuboidal cells
cells within cambium
arrangement of cambial cells
fusiform initials
horizontal rows
storied cambium
without horizontal pattern
nonstoried cambium
ray initials
grouped, short vertical rows
1 cell wide (uniseriate)
2 cells wide (biseriate)
many cells wide (multiseriate)
Secondary Xylem
types of wood cells
may contain
tracheids
vessel elements
fibers
sclereids
parenchyma
arrangement
axial system
derived from fusiform
contains tracheary elements
contains fibers
strength and flexibility
called hardwood
softwoods
woods without fiber
radial system
develops from ray initials
usually simple
woody angiosperms
contains parenchyma
arranged as
uniseriate
biseriate
multiseriate
or rays
upright cells
procumbent cells
may contain ray tracheids
growth rings
early wood
1st wood formed
less dense
late wood
wood formed later
thicker and heavier
annual ring
tree ring
shows 1yr growth
growth ring
synonym for annual ring
preferred term
heartwood and sapwood
heartwood
darker
drier
more fragrant
sapwood
lighter
inside of log
reaction wood
reaction to stress
wood becomes wider at top
Outer Bark
Cork & the Cork Cambium
Cork Cambium
produces cork cells
known as phellogen
cuboidal cells
phelloderm
layer of parenchyma cells
usually thin
outer bark
tissues outside (cork cambium)
inner bark
all secondary phloem
between vascular cambium
innermost cork cambium
responsible for secondary growth
Lenticels & Oxygen Diffusion
permeability
allowed by rounded cork cells
known as lenticels
creates oxygen diffusion
impermeability
keeps out pathgens
retains water
blocks oxygen absorption
Initiation of Cork Cambia
may arise in
epidermis
cortex
primary phloem
secondary phloem
timing
may be early
late
Secondary Phloem
formed from vascular cambium
has axial and radial system
axial
responsible for conduction
radial
nonconducting parenchyma
fibers
some alternating w/sieve tube
Anomalous Forms of Growth
secondary growth
different than dicot and gymnosperms
Roots of sweet potatoes
contain large amounts of parenchyma
phloem and xylem
almost all parenchyma
as mutation occurs
may contain hundreds cambia
Included Phloem
patches of secondary phloem
located within secondary xylem
unusual primary growth
palm trees
trunks do not taper
all primary tissue
establishment growth
increase in width
addition of adventitious roots
occurs in other monocots
