Principle Structural Planes
Gross Anatomical Features
of Wood
Cross Section Transverse
Radial
For 240 Lab 1
Tangential
Principle Structural Planes
Principle Structural Planes
Tangential Plane
• A - Quartersawn
Flatsawn - Tangential
– Radial plane on
broad face
A
B
• B - Flatsawn
– Tangential
plane on broad
face
Qartersawn - Radial
Radial Plane
General Macroscopic Features
Macroscopic Parts of Wood
•
Outer Bark –
Protection, Cells
Dead
•
Inner Bark
(Phloem) –
Conduction
downward. Many
living cells.
•
Vascular Cambium
– Produces new
secondary phloem
and secondary
xylem
Radial
Tangential
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General Macroscopic Features Sapwood
• Sapwood (Xylem)
• Heartwood (Xylem) –
– Functions: Support,
conduction, storage.
– Contains all living
cells in Xylem; mostly
dead.
– rays provide water
and nutrient transport
in from phloem.
– Function: Support.
– Used to be sapwood, now
all dead cells. Reduced
water and oxygen leads
to death of parenchyma
cells.
– Major difference between
sapwood and heartwood
not in anatomy, but in
physiology and added in
chemistry.
– Extractives may give
heartwood darker color.
General Macroscopic Features Heartwood
• Extractives Impart these Properties:
– color - black walnut and black cherry (for
decorative use)
– decay resistance - cedars, Douglass fir,
redwood, cypress
– low water permeability - Douglass fir (may
cause difficulty in drying, though)
– odor - cedars (cedar chests, closet linings)
Growth Rings – Differences Between
Early Wood and Late Wood
Earlywood
- large diameter cells
- lower density than latewood
General Macroscopic Features Heartwood
Growth Rings
• Growth Ring – a ring of wood on
a transverse surface or in a
transverse section, resulting
from periodic growth; if one
growth ring is formed during a
year it is called an annual ring
• Earlywood – that portion of a
growth increment which is
produced at the beginning of the
growing season (spring wood).
• Latewood – that portion of an
annual growth increment which
is produced during the latter part
of the growing season (summer
wood).
Growth Rings - Transition
•
The transition between early wood may be abrupt, like Red Pine (Pinus resinosa)
Latewood
- smaller diameter cells
- thicker cell walls
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Growth Rings - Transition
•
The transition may be gradual, like Eastern White Pine (Pinus strobus).
Effects of Growth Rate on Growth Rings
•
Douglas fir (Pseudotsuga menziesii)
Grain Appearance of Wood
Grain Appearance of Wood
• The arrangement and direction
of alignment of wood elements
when considered en masse.
• May be used to describe the
visual contrast between
earlywood and latewood, where
pronounced contrasts are called
uneven-grained, like southern
yellow pine, Douglas fir
(Pseudotsuga menziesii), and
eastern larch (Larix laricina).
• Do not confuse grain contrast
and grain direction, which will be
discussed later
• Commonly species with
uneven-grain have an
abrupt transition, but not
always.
• Some species like
western hemlock (Tsuga
heterophylla) may be
uneven grained with a
gradual ew/lw transition.
Grain Appearance of Wood
• Other species like
ponderosa pine
(Pinus ponderosa)
are fairly evengrained but have
an abrupt ew/lw
transition.
Wood Texture
• Texture – refers to the size and the
proportional amounts of woody elements;
in coniferous woods, the average
tangential diameter of the tracheids is the
best indicator of texture.
• Can be Fine, Medium, Coarse, and even
or uneven.
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Wood Texture
• Fine Textured woods:
– Spruce (Picea spp.)
– Eastern Red Cedar
(Juniperus virginiana)
Wood Texture
• Coarse Texture
– Sugar pine
(Pinus
lambertiana)
Macroscopic Features - Rays
• Ray Flecks in Radial Surface - Sycamore
Wood Texture
• Medium Texture
– Douglas-fir (Pseudotsuga
menziesii)
– Incense-cedar
(Calocedrus decurrens)
– Western redcedar (Thuja
plicata)
Macroscopic Features - Rays
• Rays – ribbonshaped strand of
tissue extending in
a radial direction
across the grain, so
oriented that the
face of the ribbon is
exposed a fleck on
the quarter surface.
Macroscopic
Features - Rays
• Growth Rings and
Rays in the
Tangential Plane on
Red Oak
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Resin Canals (Ducts)
• Tubular, intercellular
space sheathed by
secreting cells
(epithelium) bearing
resin in the sapwood.
• They serve a protective
function by exuding
pitch to seal off wounds
caused by mechanical
damage or boring
insects.
Resin Canals
• Resin Canals occur in all species of four
genera within the family Pinaceae:
– Pines (Pinus spp.)
– Spruces (Picea spp.)
– Larches (Larix spp.)
– Douglas fir (Pseudotsuga menziesii)
Resin Canals
• They are large,
easily seen,
numerous, and
well-distributed
in pines. They
tend to occur
singly.
Resin Canals
• In Douglas fir,
spruces, and
larches, they are
smaller, fewer, and
often occur in
tangential groups
• Western Larch
(Larix occidentalis)
Resin Canals
Resin Canals
• Resin Canals are
completely lacking in:
– Hemlocks (Tsuga spp.)
– True Firs (Abies spp.)
– Cedars (Juniperus spp., Thuja
spp.)
– Baldcypress (Taxodium spp.)
– Redwood (Sequoia spp.)
– Yew (Taxus spp.)
Douglas Fir (Pseudotsuga menziesii)
Eastern Spruce (Picea spp.)
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