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Chapter 9: - Coggle Diagram
Chapter 9:
Vascular Cambium
meristem that produces second plant body
continuously divide
fascicular cambium
regions are usually indistinguishable after 2-3 years
interfascicular cambium
never occur in flowers, seeds, or fruits
has only two types of cells
fusiform initials
long, tapered cells
periclinal wall
produces elongated cells
xylem
vessel elements
tracheids
fibers
phloem
sieve cells
companion cells
fibers
sieve tube members
anticlinal wall
ray initials
short and cuboidal
produce storage parenchyma
produce albuminous cells in gymnosperms
Arrangment of Cambial Cells
storied cambium
regular horizontal rows
nonstoried cambium
without any horizontal pattern
Secondary Xylem
Types of Wood Cells
all cells formed to the interior of the vascular cambium
secondary xylem (wood)
axial system
derived from fusiform initials
always contains tracheary elements
carry out longitudinal conduction of water through wood
fibers
give wood strength and flexibility
hardwoods
many fibers
softwoods
few fibers
may contain
tracheids
fibers
vessel elements
sclereids
parenchyma
radial system
develops from ray initials
only contains parenchyma
stores carbs and other nutrients
rays
two basic types of ray parenchyma cells
2 more items...
biseriate
uniseriate
multiseriate
Growth Rings
early wood (spring wood)
first wood formed
high proportion of wide vessels
wide tracheids (in conifers)
late wood (summer wood)
lower proportion of vessels
contains numerous fibers
thick-walled tracheids (in conifers)
annual ring
spring/summer together
diffuse porous
vessels form throughout growing season
ring porous
vessels restricted to mainly early wood
Heartwood and Sapwood
heartwood
darker in color (in most cases)
center of log
drier
more fragrant
sapwood
outer region
lighter in color
moister
new layer formed
water columns break
freezing
wind vibration
tension
wood-boring insects
tylosis
push bubbles of protoplasm through pits into vessel (forms plug)
Reaction Wood
response to lateral stress due to gravity
tension wood
grows on upper side of branch
prevents drooping
Outer Bark
Cork and the Cork Cambium
cork cambium/ phellogen
cells are cuboidal
after cell division, inner cell almost always remains cork cambium
outer cell differentiates into cork cell/phellem cell
cork cambium, layers of cork cells, phelloderm
known as periderm
outer bark
all tissues outside the innermost cork cambium
inner bark
all secondary phloem between the vascular cambium and the innermost cork cambium
Lenticels and Oxygen Diffusion
lenticels
create diffusion pathway for oxygen
Initiation of Cork Cambia
first cork cambium
more variable than that of vascular cambium
depending on species
can arise before twig or root is 1 year old
arises when region is several years old
epidermises of 40 years old
Secondary Growth in Roots
roots of conifers
woody angiosperms
vascular cambium arises
contains both ray and fusiform initials
wood produced in root
not identical to stem
Anomalous Forms of Growth
Anomalous Secondary Growth
roots of sweet potatoes
storage parenchyma increased dramatically
numerous vascular cambia arise
irregular matrix of parenchyma
few sieve tubes
some vessels
hundreds of cambia
included phloem
vascular cambium of common type arises
cambium cells stop dividing
differentiate into xylem
located between two bands of xylem
selective advantage
protection from insects/ pests
unequal activity of the vascular cambium
in some species of Bauhinia/other vines
two sectors of cambium very active
two sectors almost completely inactive
stem grows outward in two directions
becomes thin, flat, woody ribbon
selective advantage
flexibility
secondary growth in monocots
some become tree-like and "woody"
Joshua trees
secondary vascular bundles
outermost cells
develop into fibers with thick secondary walls
dragon trees
palms
Unusual Primary Growth
palm trees
trunks do not taper at tip
do not branch
trunk
primary phloem
primary xylem
derived from shoot apical meristem
hard and "woody"
vascular bundles enclosed in sheath of strong, heavy fibers
primary growth
establishment growth
Secondary Phloem
formed from vascular cambium
axial system
conduction up/down stem or root
sieve tube members
conduct <1 year
only innermost layer of phloem capable of conduction
contains sieve tube members and companion cells (in angiosperms)
sieve cells (in conifers)
radial system
ray initials
parenchyma cells
phloem rays
used for storage
