Please enable JavaScript.
Coggle requires JavaScript to display documents.
Structure of Woody Plants (Secondary Growth in Roots (root wood is similar…
Structure of Woody Plants
Vascular Cambium
Fusiform Initials
differentiates = secondary xylem or phloem
wood = inside
long tapered cells
bark = outside
anticlinal walls
thin primary wall
regular or irregular horizontal rows
Ray Initials
#
periclinal cell divisions
storage parenchyma cells
short and cuboidal cells
albuminous cells
short vertical rows
Initiation of the Vascular Cambium
continuously dividing cells = fascicular cambium
return mitosis = interfascicular cambium
meristem that produces secondary plant body
vascular cambium = > 2 years old
extended each year
distinct ages (ground = oldest)
not in flowers, fruits, or seeds
simple meristem
Arrangement of Cambial Cells
storied cambium = regular fusiform
nonstoried = irregular fusiform
specific patterns
fusiform - ray ratio = controlled
single vascular cambium per plant
vascular cambium = narrow cylinder
Secondary Xylem
Growth Rings
early wood or spring wood
early wood = many wide vessels
quiescent = summer and winter
late wood or summer wood
late wood = few vessels
late wood is strong with many fibers
end of growth = cambium dormant
early wood + late wood = 1 year of growth
growth ring = annual ring
diffuse porous = vessels located throughout
ring porous = vessels in early wood
Heartwood and Sapwood
light moist outer = sapwood
tylosis = plug
dark wood in center = heartwood
parenchyma cells die ---> sapwood to heartwood
heartwood takes awhile to develop
Types of Wood Cells
wood contains tracheids, vessel elements, fibers, sclereids, parenchyma
axial system = fusiform initials
interior = secondary xylem = wood
radial system = ray initials
axial system = tracheary elements
hardwoods = many fibers
softwoods = few fibers
parenchyma store water, carbohydrates
radial system is simple
radial system has parenchyma in rays
upright vs. procumbent cells
biseriate or multiseriate
ray tracheids = horizontal, rectangular cells
Reaction Wood
angiosperms - reaction wood = tension wood
gelatinous fibers with much cellulose
reaction wood for stress
prevent branch from drooping
conifers - reaction wood = compression wood
compression wood = rich in lignin
Secondary Phloem
axial = sieve tubes/members and companion cells
axial and radial systems
#
axial = conduction up and down
rays = parenchyma cells
rays match xylem rays
parenchyma cells = important for storage
Outer Bark
#
Lenticels and Oxygen Diffusion
rounded cork cells = o2 diffusion
diffusion areas = lenticels
oxygen absorption blocked
oxygen permeates all layers of bark
lenticels contain many layers of cells
Initiation of Cork Cambia
delayed formation of bark is possible
first cork cambium = many tissues
time of initiation is variable
young bark and old bark differ
later cork cambia deep in secondary phloem
fiber cell bark = fibrous and stringy
sclereid filled phloem = hard bark
Cork and Cork Cambium
cork cambium = phellogen
cork cambium cells are cuboidial
growth = tear or circumference growth
cork cell = phellem cell - (outer cells0
parenchyma = phelloderm
periderm = cork cells + phelloderm
cell death is critical
periderm = impermeable
periderm = temporary protection
cork cambium is short lived
several layers of cork cells build up
outermost = outer bark
outer and inner bark
Secondary Growth in Roots
root wood is similar to shoot wood
fusiform and ray initials
#
growth rates = eventually even
round vascular cambium
sapwood and heartwood
#
root wood is different than stems
root strengthened by wood fibers
small rays in roots
perennial roots form bark
Anomalous Forms of Growth
Unusual Primary Growth
palms trunks don't taper
palm trunk all primary tissue
no vascular cambium
#
establishment growth = increase of width and addition of roots
Anomalous Secondary Growth
Included Phloem
cells stop dividing = no cambium
new vascular cambium produced
eudicots
included phloem = inbetween two bands of xylem
protects phloem
Unequal Activity of the Vascular Cambium
advantageous flexibility
adaptive growth
woody vines = 2 active and 2 inactive
stem widens = larger conducting capacity (same flexibility)
Sweet Potato Roots
numerous vascular cambia
irregular matrix of parenchyma
increased storage
multiple vascular cambia = fast production of storage
Secondary Growth in Monocots
Joshua trees, palms, and dragon trees
Joshua and dragon = no conducting cells
not much secondary growth
secondary vascular bundles
branching becomes feasible