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Structure of Woody Plants - Coggle Diagram
Structure of Woody Plants
Vascular Cambium
Initiation of the Vascular Cambium
vascular cambium=
a meristem that produces secondary plant body
fascicular cambium
woody plants have this
cells continue to divide, never mature
interfascicular cambium
mature parenchyma that resume mitosis
two cell types
fusiform initials
ray initials
Fusiform Initials
long, tapered cells
longitudinal cell division with a wall parallel to the circumference of the cambium
Periclinal wall
longitudinal cell division perpendicular to cambium surface
Anticlinal wall
increases number of cambial cells
Arrangement of Cambial Cells
ray and fusiform initials organized in specific patterns
fusiform initials in regular horizontal rows
storied cambium
fusiform initials irregularly without horizontal pattern
nonstoried cambium
Ray Initials
short, cuboidal
periclinal cell divisions
one remains cambial ray initial
one becomes either xylem or phloem parenchyma
Secondary Xylem
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Types of Wood Cells
very similar structures
all cells interior to VC
"wood"
contains only cell types from primary xylem
ray tracheids
horizontal rectangular cells
secondary xylem cells dependent on initials
axial system from fusiform initials
always contains tracheary elements
hardwoods
radial system developed from ray initials
few to no fibers
softwoods
two basic types of ray parenchyma cells
upright cells
procumbent cells
Growth Rings
early wood=spring wood
first wood formed in a growth cycle
contains a high proportion of wide vessels
late wood
lower proportion of vessels
annual ring
where early wood and late wood of different growth seasons meet
diffuse porous
the wood of a growth ring with vessels thru it
ring porous
vessels restricted mainly to early wood
Heartwood and Sapwood
heartwood
center of a log
drier and more fragrant
used as storage for waste products
sapwood
lighter, moister outer region
living cells that function in transport and division
Reaction Wood
growth done in response to stress
caused by weight and gravity
Secondary Phloem
"inner bark"
formed from the vascular cambium
has axial and radial system
Outer Bark
Cork and the Cork Cambium
reactivation of cells results in a new cambium
cork cambium=phellogen
inner cell remains as cork cambium
outer cell becomes cork cell
cork cell=phellem cell
production of inside layer=phelloderm
whole kit and caboodle=periderm
tissues outside the innermost cork cambium=outerbark
secondary phloem between VC and innermost cork =inner bark
Lenticels and Oxygen Diffusion
cork leads to lower gas exchange
rounded cells do not fit together tightly
results in Lenticels
Initiation of Cork Cambia
varies widely across species
some shed epidermis quickly, some after decades
cork can begin after days or months
Secondary Growth in Roots
roots undergo secondary growth just like stems
secondary VC has same star shape
root VC has ray and fusiform initials
wood produced in root is very similar to shoot
perennial roots form bark
cork cambium arises in pericycle
causes endodermis out to be shed
