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Chapter 8: Structure of Woody Plants (Anomalous Forms of Growth (included…
Chapter 8: Structure of Woody Plants
Vascular Cambium
initiation of the vascular cambium
vascular cambium
meristems that produce secondary plant body
modern ferns
absent in all species
gymnosperms
present in all species
basal angiosperms
present in many species
many are herbs
eudicots
present in many species
many are herbs
monocots
absent in all species
some have anomalous secondary growth
fascicular cambium
cells continue to divide instead of maturing
interfascicular cambium
some mature parenchyma cells
between vascular bundles
resume mitosis
two types of cells
fusiform initials
long tapered cells
ray initials
short, less cuboidal cells
arrangement of cambial cells
organized in a specific pattern
ray initials
grouped together in short vertical rows
fusiform initials
regular horizontal rows
Secondary Xylem
types of wood cells
no new cells
contain
tracheids
vessel elements
fibers
sclerids
parenchyma
only difference is
arrangement of cells
axial system
derived from fusiform initials
contains tracheas and/or vessel elements
angiosperm woods contain
large amounts of fibers
making them strong and tough
useful for construction
hardwoods
lacks fibers
radial system
derived from ray initials
tracheids and parenchyma are present
growth rings
early wood
first time wood is formed
also called spring wood
high proportion of wide vessels
late wood
also called summer wood
lower proportion of vessels
stronger
annual ring
how to tell the age of a tree
1 ring = 1 year
growth ring
heartwood and sapwood
center is darker than outside
drier wood
dark wood
heartwood
lighter, moister region
sapwood
Secondary Phloem
formed from vascular cambium
has axial and radial system
axial system
responsible for conduction of up and down the stem or root
Outer Bark
cork and cork cambium
cork cambium
also called phellogen
cuboidal cells
produced into a mature parenchyma layer
phellloderm
outer bark
all tissues outside the innermost cork cambium
inner bark
secondary phloem between vascular cambium and innermost cork cambium
Anomalous Forms of Growth
roots of sweet potatoes
parenchyma is increased dramatically
included phloem
several eudicots
vascular cambium arises
produces ordinary secondary xylem and phloem
unequal activity of the vascular cambium
ordinary growth
all areas have equal activity
secondary growth in monocots
secondary vascular bundles
parenchyma cells undergo rapid cell division and produce narrow cells
unusual primary growth
palm trees
trunks dont taper at the tips
