The Law & The Prophets/Profits Rhys Jones, Adrian Bowyer & Erik de Bruijn.
Tree Growth and Wood Formation Basic macroanatomy of a tree stem How a tree grows FW1035 Lecture 1...
-
date post
21-Dec-2015 -
Category
Documents
-
view
216 -
download
0
Transcript of Tree Growth and Wood Formation Basic macroanatomy of a tree stem How a tree grows FW1035 Lecture 1...
Tree Growth and Wood Formation
• Basic macroanatomy of a tree stem
• How a tree grows
FW1035Lecture 1Bowyer et al, Chapter 1
Coast RedwoodSequoia sempervirens
Tallest Living Individual: 380 feet (~2000 yo)
Weight: up to ~2.7 million lbs
Saturn V RocketHeight: 383 feetWeight: 6.7 million lbs
Mountain AshEucalyptus regnans
Tallest Living Individual: 330 feet (~400 yo)
“World’s tallest flowering plant.”
Heartwood
Sapwood
Stem Macroanatomyand Transverse Anatomical Directions
RadialTangential
Vascular Cambium
Longitudinal Direction is perpendicular to the transverse directions.
Heartwood
Sapwood
Stem Macroanatomyand Transverse Anatomical Directions
RadialTangential
Vascular Cambium
Longitudinal Direction is perpendicular to the transverse directions.
Rays in Wood
• Ray cells are elongated in the radial direction
• Width, height, density, and appearance vary - useful for ID
Annual Ring
Latewood
Earlywood
Function: Transport from the phloem towards the pith.
Major Tissues in the Tree Stem
Outer Bark• Protection
Phloem (Inner Bark)• Transport (down)
Cambium• Radial growth
Xylem (Wood)• Transport (up) and
mechanical support
Transport in Trees
Sap - a water solution of sugars, minerals, O2, and growth regulators
• Roots – water, dissolved minerals, other nutrient uptake
• Xylem - flow up toward leaves
• Phloem - downward flow (sugars
and regulators) • Rays - flow towards the center of
the tree (pith)
Growth Tissues - “Meristematic Tissues”
Diameter• Diameter growth occurs at
the lateral meristem (vascular cambium)
• Tissues formed are “secondary tissues”
– secondary xylem
– secondary phloem
Height• Height growth and branch
shoot elongation occurs only at their tips
• Apical meristem
• Apical meristems only produce “primary tissues”
– primary xylem
– primary phloem
Meristem = Plant tissue which contains cells that have the capacity to divide to make new cells.
The Apical Meristem
Epidermis• single layer of thick, waxy cells
that prevents moisture loss
Procambium• meristematic region that provides
growth• cell division produces primary
phloem and xylem• further differentiation gives rise to
the vascular cambium• primary xylem and pith is different
from secondary xylem (wood)
Vascular Cambium
The Vascular CambiumLateral meristematic region • Division of cells here produces
secondary xylem and secondary phloem tissues
• Diameter expansion forces tangential elongation of phloem cells
• Epidermis and primary phloem layers eventually fall off
• Dead phloem cells compose the outer bark
Vascular Cambium Two Cell Types • Fusiform Initials - divide to
produce new xylem or phloem cells that have longitudinally elongated shapes
• Ray initials - short, rounded cells that divide to produce new xylem or phloem ray cells.
Cell Division Direction
Cells can divide 2 ways:• Periclinal division - cells
divide along the longitudinal axis of the stem (responsible for diameter growth of cambium)
• Anticlinal division - cells divide in radial direction (responsible for circumference growth of tree, in general)
After Periclinal division, one cell remains a cambial initial, the other a xylem or phloem “mother” cell. Mother cells may divide several more times before differentiating into mature xylem or phloem cells, or immediately differentiate into a xylem or phloem cell without further division.
Periclinal Division