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Ch. 8 Structure of Woody Plants (Secondary Phloem # (axial system…
Ch. 8 Structure of Woody Plants
Concepts
primary tissues
meristem
epidermus
cortex
vascular bundles
pith
leaves
secondary tissue
wood
move carbohydrates downwards, minerals upward
bark
Vascular Cambium
Initiation of the Vascular Cambium
fascicular
in vascular bundles
interfascicular
between vascular bundles
Fusiform Initials
periclinal wall
wall parallel to the cambium
anticlinal walls
perpendicular to cambium
long, tapered cells
Ray Initials
short and cuboidal
storage parenchyma
gymnosperms
albuminous cells
Arrangement of Cambial Cells
storied cambium
regular, horizontal rows
nonstoried cambium
no horizontal pattern
Secondary Xylem
Types of Wood Cells
secondary xylem
wood
axial system
derived from fusiform initials
radial system
derived from ray initials
hardwood
large amounts of fibers
softwood
few or no fibers
ray parenchyma cells
upright cells
procumbent cells
may contain ray tracheids
Growth Rings
late wood
lower proportion of vessels
early wood
first wood formed
annual ring/growth ring
one years growth
early wood + late wood
diffuse porous vs. ring porous
diffuse
growth ring has vessels throughout it
ring
vessels restricted to early wood
Heartwood and Sapwood
heartwood
dark wood
sapwood
light, moist wood
tylosis
plug of parenchyma cells
Reaction Wood
branches/trunks aren't verticle
angiosperms
upper side of branch
tension wood
rich in cellulose
little/no lignin
Secondary Phloem
#
formed from vascular cambium
axial system
conduction up and down stem/root
radial system
phloem rays
only parenchyma cells
Outer Bark
Cork and the Cork Cambium
aka phellogen
cork cell
outer cell
aka phellem cell
phelloderm
layer of parenchyma
periderm
outer bark
all tissues outside innermost cork cambium
inner bark
all secondary phloem between vascular and cork cambium
Lenticels and Oxygen Diffusion
lenticels
regions of aerenchymatous cork
when new cork cambium arises interior to ^
Initiation of Cork Cambia
first cork cambium arises before twig is 1yr.
slow growth = cork cambia 10yr. intervals
usual growth = cork cambia 1-2yr. intervals
Secondary Growth in Roots
vascular cambium
#
same star shape as primary xylem
contains ray and fusiform initials
cork cambium
arises from pericycle
layer or two of phelloderm
lenticels
Anomalous Forms of Growth
Anomalous Secondary Growth
Roots of Sweet Potatoes
stored parenchyma increases dramatically
can contain hundreds of cambia
Included Phloem
#
located between two bands of xylem
type of secondary phloem
Unequal Activity of the Vascular Cambium
two vectors are active and two vectors are not
Secondary Growth in Monocots
Joshua and dragon tress
vascular cambium outside the outermost vascular bundles
secondary vascular bundles
produced by rapid parenchyma division
xylem and phloem
unusual Primary Growth
establishment growth
form of no primary growth
palm tree
all primary growth
both formed from vascular cambium
arises the same
type of secondary phloem
