2. Tree growth begins with photosynthesis to produce new
wood when the growing season begins.
3. Trees grow upward and outward (including root tips), but…
… tree growth actually
begins in the crown and
moves downward due to the
growth regulator, auxin.
Like
“melting
wax” !!
11. Definitions:
Cambium: the growing (generative) layer between the xylem and phloem.
Xylem: principle strengthening and water conducting tissue of the stem,
roots, and branches.
Phloem: inner bark, principal function to distribute manufactured
foodstuffs.
Bark: dead, outer tissue that protects the cambium from the external
environment and exposure to pathogens and physical injury.
Vessel: the composite, tube-like structure found in hardwoods from the
fusion of cells in a longitudinal column.
Fiber: an elongated cell with pointed ends and a thick or infrequently thin
wall.
Rays: ribbon-shaped tissue extending in a radial direction across the grain
of the wood.
15. The Wood Cell:
1. Holocellulose
a. alpha-cellulose (40-50%) = non-soluble =
long-chain polymers (glucose)
b. hemicellulose (20-35%) = readily soluble =
short-chain polysaccharides
2. Lignin (15-35%) – non-carbohydrate materials in
cell wall, very complex chemical structure.
3. Numerous Extractives – can be removed!
a. tannins
b. oils and resins
c. other complex organic compounds