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Chapter 9 Structure of Woody Plants - Coggle Diagram
Chapter 9 Structure of Woody Plants
Concepts
primary tissues - epidermis, cortex, vascular bundles, pith, and leaves.
make up primary plant body
secondary tissues - wood (secondary xylem) and bark (secondary phloem and cork).
make up secondary plant body
Vascular Cambium
Initiation of the Vascular Cambium
vascular cambium - one of the meristems that produces the secondary plant body
fascicular cambium - cells located between metaxylem and metaphloem in vascular bundle
in herbaceous plants these cells stop dividing
interfascular cambium - formed by mature parenchyma cells between vascular bundles that resume mitosis.
this connects to fascicular cambia
Made of two cell types
Fusiform Initials
long tapered cells
when cells divide one stays a fusiform initial and other differentiates into secondary xylem or phloem
Ray Initials
short and cuboidal
Arrangement of Cambial Cells
ray cells grouped uniseriate, biseriate, or multiseriate
fusiform initials grouped storied cambium (horizontal rows) or nonstories cambium (without any horizontal pattern)
Secondary Xylem
Types of Wood Cells
secondary xylem - all cells formed to the interior of the vascular cambium; wood.
secondary xylem has all cell types in primary xylem but no new ones.
arrangement reflects that of fusiform and ray initials
axial system - derived from fusiform initials
radial system - develops from ray initials
Growth Rings
vascular cambium is quiescent during stress
early wood - first wood formed aka spring wood
needs lots of wide vessels
Late wood - aka summer wood. lower proportion of vessels
growth of early and late wood together forms an annual ring
diffuse porous - growth ring has vessels throughout
ring porous - species with vessels restricted to early wood.
Heartwood and Sapwood
Heartwood - darker wood at the center of a log
forms after parenchyma cells die
Sapwood - moister, lighter outer wood of log
made every year
Tylosis - plug that blocks dead vessels
Reaction Wood - wood that prevents drooping using the fibers contained in them.
Secondary Phloem
also has axial and radial system
Outer Bark
Cork and the Cork Cambium
cork cambium / phellogen - cambium formed by reactivation of parenchyma cells during circumferential stretching
all cells are cuboidal
Inner cell remains cork cambium. Outer differentiates into cork cell
both combined is periderm
all tissues outside cork cambium are outer bark
all secondary phloem between vascular cambium and innermost cork cambium is inner bark
Lenticels and Oxygen Diffusion
lenticels - regions of aerenchymatous cork
Inititation of Cork Cambia
timing initiation is variable
begins before twig or root is 1 year old
Anomalous Forms of Growth
Anomalous Secondary Growth - alternative types of cambium structure and activity
Roots of Sweet Potatoes
anomalous secondary growth increases amount of storage parenchyma
xylem and phloem are almost purely parenchyma
Included Phloem
vascular cambium arises and secondary xylem and phloem is produced. Cambium stops dividing and differentitates into xylem.
Cambium no longer exists
Oldest secondary phloem reactivates and differentiates into new vascular cambium
type of phloem located between two bands of xylem
Unequal Activity of the Vascular Cambium
stem doesnt grow equally.
causes strangely shaped areas
Secondary Growth in Monocots
different from in gymnosperms
parenchyma cells produce narrow cells that differentiate into secondary vascular bundles
Unusual Primary Growth
Trunks of palm trees don't taper
vascular cambium never develops and true wood and secondary phloem don't occur
