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Structure of Woody Plants (Vascular Cambium (Initiation of Vascular…
Structure of Woody Plants
Vascular Cambium
Initiation of Vascular Cambium
cells do not undergo cell cycle arrest
continue to divide
give rise to fascicular cambium
interfascicular cambium
mature parenchyma cells comes out of cell cycle arrest
connects each side with fascicular cambium
extended each year
contains both primary and secondary tissue
represent distinct ages within the tree
close to the tip of axes
younger
near the ground
oldest
two types of cells
ray initials
short, cuboidal
storage parenchyma cells
albuminous cell in gymnosperm
goes through periclinal cell division
one continues to be cambial ray initial
other give rise to secondary xylem or phloem
fusiform initials
long, tapered cells
140-462 microns in dicots
700-8700 microns in conifers
goes through longitudinal cell division
one continues to be fusiform initial
other give rise to secondary xylem or phloem
anticlinal wall
located perpendicular to the cambium's surface
periclinal wall
wall parallel to the circumference of cambium's surface
Arrangement of Cambial Cells
organized in specific patterns
Ray initials
grouped together in short vertical rows
can be
uniseriate
one cell wide
biseriate
two cell wide
multiseriate
many cells wide
Fusiform initials
regular horizontal rows
storied cambium
rare
occur in few eudicots species
tend to be dhor
irregular
nonstoried cambium
Secondary Xylem
Types of Wood Cells
#
contains same types of cells found in primary xylem
may contain
tracheids
vessel elements
fibers
sclereids
parenchyma
axial system
derived from fusiform initials
contain tracheary elements
blood vessels
tracheids
carry out longitudinal conduction of water
gives wood strength and flexibility
radial system
#
derived from ray initials
simple
angiosperms
contain only parenchyma
store carbohydrates and nutrients
upright cells
procumbant cells
arranged in rays
forms inside the vascular cambium
Growth Ring
early wood
first wood formed
spring wood
have high proportion of wide vessels
late wood
thick cuticle
less transpiration
summer wood
stronger, provides support
annual ring
early wood and late wood
reaction wood
produced under stress by plants
called tension wood in angiosperm
contain gelatinous fibers with cellulose rich wall
prevent branch from dropping
eccentric growth ring
compression wood in conifers
Secondary Phloem
Axial system
responsible for conduction up and down the stem or root
contains sieve tube members and companion cells
fibers and non conducting parenchyma
radial system
consist only parenchyma cells
storage
albuminous cells in conifers
Outer Bark
Cork and Cork Cambium
Cork cambium
also called phellogen
differ greatly from vascular cambium
Cork cell
also called phellem celll
outer cell
periderm
includes phellogen, phellem and phelloderm
outer bark
tissues outside of innermost cork cambium
inner bark
secondary phloem between vascular cambium and innermost cork cambium
Lenticels and Oxygen Diffusion
inter cellular space for diffusion pathway for oxygen
contain more layers of cell
Initiation of Cork Cambia
first cork cambia arises before twig is 1 years old
detectable in stems
color changes from green to tan
may take several years in some species
Secondary Growth in Roots
vascular cambium arises
parenchyma cells become mitotically active
paricyle cell near protoxylem divides
conductivity
takes in and store water rapidly
pericycle
endodermis, cortex and epidermis shed
cork cells provides protection
Anomalous Forms of Growth
Secondary Growth
alternative cambia produce secondary body
Roots of sweet potatoes
new vessels surrounded by new cambium
parenchyma
higher storage capacity
more cells production
Vascular cambium
#
unusual activity
stem grow in 2 directions
provides flexibility
adaptive
Primary Growth
unusual
establishment growth
increases in width
adventitous roots addition
occurs in palms
Shows Similarity Connection
Similar cells involved
Functional Connection
