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Structure of Woody Plants (growth rings 9781284096040_CH08_FIGB03_01…
Structure of Woody Plants
vascular cambium
one of the meristems the produce the secondary plant body
fascicular cambium
cells between the metaxylem & metaphloem never undergo cell cycle arrest; they divide w/o maturing
interfascicular cambium
when mature parenchyma cells btwn vascular bundles come out of cell cycle arrest & resume mitosis
fusiform initials
&
ray initials
are the only cells that make up the vascular cambium
fusiform initials
long, tapered cells
periclinal wall
undergoes longitudinal cell division w/ a wall parallel to the circumference of the cambium
anticlinal walls
occasionally divide longitudinally this way, thereby increasing the # of cambial cells
w/o these divisions, cambial cells would be stretched wider circumferentially & could not function
storied cambium
cells occur in regular horizontal rows
nonstoried cambium
cells irregularly, w/o any horizontal pattern
ray initials
short & more/less cuboidal
undergo periclinal cell division
produce short cells, mostly just storage parenchyma
grouped together in short vertical rows btwn 1,2, or many cells wide
types of wood cells
secondary xylem
also known as wood
axial system
derived from the fusiform initials
hardwoods
contain large amounts of fibers, making them strong, tough, & useful for construction
softwoods
few or no fibers & have a softer consistency
radial system
develops from the ray initials
upright cells
&
procumbent cells
two basic types of ray parenchyma cells
upright cells
have direct connections to the axial cells
procumbent cells
have no no direct connection w/ axial cells
ray tracheids
in addition to ray parenchyma cells these may occur
horizontal, rectangular cells that have secondary walls, circular bordered pits, & protoplasts
growth rings
early wood
1st wood formed, must have high proportion of wide vessels, or wide tracheids
late wood
cuticle has thickened, transpiration is less, & large #s of newly formed vessels are conducting rapidly
annual ring
early & late wood make up 1 year's growth
growth ring
when a tree fails to grow & produce a ring
diffuse porous
vessels located throughout growth rings
ring porous
vessels are restricted (mainly in early wood)
heartwood
dark wood
sapwood
lighter, moister outer wood region
reaction wood
produced due to stress
prevents wood from drooping & in some cases can elevate it
secondary phloem
formed from vascular cambium
axial system
responsible for conduction up & down the stem or root
radial system
the same ray initials of xylem rays produce phloem rays
phloem ray consist only of parenchyma cells that are used for storage (even more important here than in xylem)
outer bark
cork cambium/phellogen
all cells are cuboidal & inner cell almost always remain cork cambium
cork cell/phellem cell
outer cell differentiates into this
phelloderm
cork cambium may produce a cell or two to the inside that mature into this layer of parenchyma
periderm
all layers of cork cells & phelloderm (if any)
lenticels
creates diffusion pathway for oxygen, more active, contain more layers of cells & protrude outward
outer bark
all tissues outside the innermost cork cambium comprise
inner bark
all secondary bwtn the vascular cambium & innermost cork cambium
anomalous secondary growth
alternative cambia produce secondary bodies that differ from the common type
included phloem
secondary phloem located between two band of xylem
secondary vascular bundles
parenchyma cells undergo rapid division & produce narrow cell that differentiate into this & contain both xylem & phloem
establishment growth
form of primary growth where the palms become increased in width & addition of adventitious roots
