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Chapter 8: Structure of Woody Plants (Vascular Cambiam 4d0d62f1a18868793ec…
Chapter 8: Structure of Woody Plants
Vascular Cambiam
fusiform initials
long, tapered cells
periclinal walls
elongate cells are produced here
anticlinal walls
divide longitudinally
perpendicular to cambium's surface
thin primary walls
plastids are present as proplastids
ray initials
similar to fusiform initials
less cuboidal
shorter
undergo periclinal divisions
produce short cells
Initiation of vascular cambium
fascicular cambium
cells divide instead of maturing
interfascicular cambium
connects on each side with fascicular cambia
two cell types
fusiform initials
ray initials
arrangement of cambial cells
storied cambium
regular horizontal rows
nonstoried cambium
irregular, non horizontal pattern
Seconday Xylem
#
types of wood cells
arrangement
axial system
#
derived from fusiform initials
always contains tracheary elements
cell types present in wood
conifers
fibers (rare)
parenchyma (rare)
tracheids
eudicots
tracheids
vessels
fibers
parencyma
radial system
#
develops from ray initial
cell types present in wood
conifers
ray tracheids
ray parenchyma
eudicots
ray parenchyma cells
upright cells
procumbent cells
heartwood and sapwood
sapwood
light
moist
new layer formed each year
heartwood
dark
dry
fragrant
growth rings
vessel differences
diffuse porous
ring porous
age
early wood
also known as spring wood
high proportions of wide vessels
late wood
low proportions of wide vessels
larger and heavier
reaction wood
develops mostly on upper side of branch
growth rings are eccentric
forms as a response to stress
Seconday Phloem
#
formed from the vascular cambium
has axial and radial systems
Outer Bark
cork cambium
also called phellogen
differs greatly from vascular cambium
cuboidal cells
cells differentiate into cork cells
layers of these are called periderm
offers temporary protection
roots and stem grows interior to it
bark
inner
outer
lenticels and oxygen diffusion
lenticels
regions of aerenchymatous cork
contain more layers of cells
protrude outward
initiation of cork cambium
timing is variable
barks of different ages are dramatically different
Anomalous Forms of Growth
anomalous secondary growth
included phloem
secondary phloem
located between two bands of xylem
protects phloem from insects
unequal activity of the vascular cambium
two sectors are active; two sectors are inactive
advantage: flexibility
example
Bauhinia
roots of sweet potatoes
increased storage parenchyma
many vascular cambium
secondary growth in monocots
vascular cambium arises outside the outermost vascular cambium bundles
conducting cells are absent
parenchyma cells undergo division
differentiate into secondary vascular bundles
unusual primary growth
establishment growth
increased width
addition of adventitious roots in palms
form of primary growth
occurs in monocots
shoots and roots can become longer
Secondary Growth in Roots
roots of conifers and woody angiosperms
roots and vascular cambium contain
ray initials
fusiform initials
perennial roots
form bark
lenticels can occur
