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Ch 8 Structure of Woody Plants (Vascular Cambium (Initiation of the…
Ch 8 Structure of Woody Plants
Vascular Cambium
Initiation of the Vascular Cambium
one of the meristems that produce secondary plant body
woody species
fascicular cambium
fascicle= bundle
continue dividing
interfascicular cambium
connects on each side with fascicular cambia
only has two types of cells
fusiform initials
ray initials
Fusiform Initials
long taper cells
parallel cell division
periclinal wall
perpendicular cell division
anticlinal walls
increase number of cambia cells
Ray Initials
short and cuboidal
similar to fusiform
produce storage parenchyma
Arrangement of Cambial Cells
storied cambium
regular horizontal rows
evolved more recently
nonstoried cambium
without any horizontal pattern
Secondary Xylem
Types of Wood Cells
secondary xylem=wood
all cells formed interior to vascular cambium
axial system
derived from the fusiform
tracheary elements
longitudinal conduction of water through wood
radial system
develops from ray initials
hardwood
wood of all basal angiosperms and eudicots
softwoods
few or no fibers
two basic types of ray parenchyma
up right cells
procumbent cells
no direct connection with axial cells
Growth Rings
early wood
first wood formed
annual ring/ growth ring
1 year growth
ring pores
vessels restricted to early wood
diffuse porous
vessels located throughout it
Heartwood and Sapwood
heartwood
dark wood
sapwood
lighter, moister outer region
Reaction Wood
response to stress
Secondary Phloem
formed from vascular cambium
has axial and radial system
axial system
responsible for conduction up and down stem or root
Outer Bark
Cork and the Cork Cambium
cork cambium/phellogen
new cambium
cork cell
outer cell
phelloderm
cell matures into layer of parenchyma
periderm
layers of cork cells
Lenticels and Oxygen Diffusion
lenticels
regions of aerenchymatous
Initiation of Cork Cambia
timing is more variable
Secondary Growth in Roots
root vascular cambium has ray and fusiform initials
perennial roots also form bark
storage capacity of a woody root can be increased
Anomalous Forms of Growth
Anomalous Secondary Growth
alternative cambia produce secondary bodies that differ from common type
sweet potatoes
storage roots
Unusual Primary Growth
palm trees
establishment growth
form of primary growth
