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Structure of Woody Plants (Secondary Xylem (Growth Rings (early wood (high…
Structure of Woody Plants
Secondary Xylem
Growth Rings
early wood
high proportion of wide vessels
late wood
lower proportion of vessels
annual ring
early wood+late wood
diffuse porous
has vessels located throughout it
ring porous
vessels restricted to early wood
Heartwood and Sapwood
heartwood
dark wood
sapwood
moister outer region
Types of Wood Cells
radial system
ray initials
axial system
fusiform initials
tracheary elements
carry out longitudinal conduction
water through wood
hardwoods
basal angiosperms and eudicots
softwoods
harder than hard woods
ray tracheids
horizontal, rectanular cells
Reaction Wood
stress
upper side of branch
tension wood
Outer Bark
Cork and the Cork Cambium
phellogen
all cells are cuboidal
after division
cell always remain cork cambium
outer cells
differentiate into cork cells
periderm
cork cells, cork cambium, phelloderm
maturing cork cells
increase in volume
Vascular Cambium
Fusiform Initials
long, tapered cells
140-462 um in dicots
700-8,700 um in conifers
2 elongate cells
differentiates into a cell of
secondary phloem
secondary xylem
one continues fusiform initial
Ray Initials
short and cuboidal
undergo periclinal cell divisions
daughter cells
one differentiating
phloem parenchyma
xylem parenchyma
one remains cambial ray
Initiation of the Vascular Cambium
meristem
secondary plant body
fascicular cambium
"fascicle" = bundle
2 types of cells
fusiform initials
ray initials
Anomalous Forms of Growth
Unusual Primary Growth
vascular bundles
Anomalous Secondary Growth
produce secondary bodies
establishment growth
increase in width
addition of adventitious roots
Secondary Growth in Roots
undergo secondary growth
vascular cambium arises
the new vascular cambium
same star shape
as primary xylem
Secondary Phloem
formed from the vascular cambium
