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Chapter 8 (Vascular Cambium (fusiform initials (cambial cells (narrow…
Chapter 8
Vascular Cambium
initiation of vascular cambium
vascular cambium
simple meristem
produces plant body
2 types of cells
fusiform initials
ray initials
must be extended each year
woody species
cells between mextaxylem and metaphloem
continue to divide
constitute
fascicular cambium
cells between vascular bundles
come out of cell cycle arrest
resume mitosis
form
interfasicular cambium
connects to each side of the
fascicular cambium
Ray initials
short and cubical
mostly just storage parenchyma
undergo periclinal cell divisions
daughter cells
cambial ray
xylem parenchyma (inner cells)
or phloem parenchyma cells (outer cells)
and in
gymnosperms
albuminous cells
fusiform initials
cambial cells
narrow daughter cells
mature into secondary xylem
cambial cells pushed outward
undergoes longitudinal cell division
with peridinal wall
produces two alginate cells
secondary xylem
or secondary phloem
fusiform initial
thin primary walls
plastids = propplastids
long tapered cells
arrangement of cambial cells
non storied cambium
haven’t evolved more recently
single tree or shrub
has only a single
vascular cambium
each section forms narrow cylinder
storied cambium
evolved more recently
Secondary Xylem
types of wood cells
secondary xylem cells
axial system
fusiform initials
always contain
treachery elements
woody andiosprems
parenchyma
arranged as mulitseriate masses
rays
ray parencyma
2 more items...
radial system
ray initials
cells formed to interior of vascular cambium
secondary xylem
wood
contain
sclereids
parenchyma
fibers
vessel elements
growth rings
the first ring formed
is early wood
later
cuticle thickens
newly formal vessels
wood [produced at this point
is late wood
plus annual wood is
annual ring
must have
high proportion of
wide vessels
heartwood and sapwood
wood parenchyma cells
push bubbles of protoplasm through pits
into vessel
form a plug
tylosis
lighter/ moister outer region
sapwood
dark wood
heart wood
new layer of sap wood
every year
by vascular cambium
an average one annual ring is converted to heart wood each year
reaction wood
not vertical
gravity causes lateral stress
in response
most plants reproduce
reaction wood
conifers
compression wood
in angiosperms
develop mostly
tension wood
gelatonia fibers
fibres exert tension
to keep tree from developing
outer bark
lenticels and oxygen diffusion
regions of arenchymatous cork
lenticels
have more layers of cells
at bases of the cracks in the bark
bark becomes permeable to oxygen
cork cells rounded
rounded cells
cannot fit tightly together
intercellular spaces penetrate
cork layer
creating pathway for oxygen
initiation of cork cambia
far more variable
than vascular cambium
in some species
cork cambium
arises before
twig or root
is a year old
outer species
frist cork cambium
from only when region is several years old
cork and cork cambium
secondary phloem
new cambium
cork cambium
aka phellogen
inner cell
remains same
outer cell
cork cell
phellem cell
all tissues outside
inner most cork cambium compromise
outer bark
differs from vascular cambium
all secondary phloem
between vascular cambium an dinner most cork cambium
inner bark
many produce a cell or two
into a layer of parenchyma
called phelloderm
secondary phloem
formed from
vascular cambium
axial system
conduction
up and down the stem or root
angiosperms
sieve tube members
companion cells
conifers
sieve cells
radial system
