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Structure of Woody Plants (Anomalous Forms of Growth (included phloem…
Structure of Woody Plants
Vascular Cambium
Initiation of the vascular camobium
Interfascicular cambium
Between vascular bundles
some mature parenchyma cells
resume mitosis
Two types of cells:
Fusiform initials
Long tapered cells
Ray initials
short, less cubodial cells
Fascicular cambium
Cells continuously divide instead of maturing
Vascular cambium
Monocots
Absent in all species
some anomalous 2ndary growth
Eudicots
many are herbs
present in all species
Gymnosperms
present in all species
Meristems produce 2ndary plant body
absent in all species
Modern Ferns
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present in many species
many are herbs
Arrangement of cambial cells
Ray initials
grouped together in short vertical rows
Fusiform
regular horizontal rows
Organized in a specific pattern
outer bark
cork and cork cambium
cork cambium
produced into a mature parenchyma layer
phelloderm
inner bark
2ndary phloem
between vascular cambium and intermost cork cambium
outer bark
all tissues outside innermost cambium
also called phellogen
cuboidal cells
Anomalous Forms of Growth
unusual primary growth
palm trees
trunks don't taper at tips
unequal activity vascular cambium
ordinary growth
all areas have equal activity
roots of sweet potatoes
parenchyma increased dramatically
included phloem
vascular cambium arises
several eudicots
produces ordinary 2ndary xylem and phloem
2ndary growth in monocots
2ndary vascular bundles
parenchyma cells undergo rapid division
produce narrow cells
secondary xylem
growth rings
annual ring
growth ring
tell age of tree
one ring=one year
early wood
high proportion of wide vessels
first time wood is formed
"spring wood"
late wood
"summer wood"
lower portion of vessels
stronger
types of wood cells
radial system
derived from ray initials
tracheids and parenchyma present
only differnce is
arrangement of cells
no new cells
contain
parenchyma
fibers
tracheids
vessel elements
schlerids
axial system
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angiosperms wood contain
large amount of fibers
making them strong and tough
useful for construction
derived from fusiform initials
contains tracheas and/or vessel elements
hardwoods
lacks fibers
heartwood and sapwood
dark wood
heartwood
lighter, moister region
sapwood
center, darker than outside
drier wood
2ndary phloem
fprmed from vascular cambium
has axial and radial system
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responsible for construction of up and down the stem or root
