wood anatomy exam 1

environmental issue of illegal wood

affecting endangered and vulnerable species, unsustainable (causing deforestation), damages biodiversity

criminal impacts of illegal wood

lost tax revenue, funds organized crime

commercial impacts of illegal wood

price depression/lost sales, consumer fraud, perception of lesser quality

Convention on International Trade in Endangered Species (CITES)

international treaty for endangered species

Lacey Act

domestic law for living species

unknown

the extent of illegal wood is

trees

single supporting stem

shrubs

can have multiple supporting stems

vines

climbers, use other plants for structure

characteristics of wood

anisotropic, hygroscopic, heterogenous, biological material

transverse plane

aka [X]; looking down onto the tree

tangential plane

aka [T]; slicing down the side of a tree, cutting rays in half

radial plane

aka [R]; cutting into the tree towards the pith, cutting into rays

up

direction of fluid movement

down

direction of nutrient movement

order of materials

outer bark, phloem (inner bark), cambium, xylem (sapwood), xylem (heartwood), pith

heartwood

darker in many species, contains extractives, all cells are dead

sapwood

contains living cells, transitions to heartwood as wood ages

rays

horizontal, tubular passages that conduct sap through the radius of the trunk

primary growth

produced by apical meristems, which lengthen stems and roots

secondary growth (cambium)

produced by lateral meristems, which thickens the roots and shoots; vascular and cork cambium

phases of cell development

cell division, enlargement, cell wall thickening, lignification (hardening)

cell division

cambium initials form fusiform or ray initials; cells inside cambium become xylem, cells outside cambium become phloem (periclinal division)

fusiform initials

become longitudinal cells

ray initials

become ray cells

enlargement

fusiform initials divide to form xylem/phloem mother cells

cell wall thickening

primary wall, secondary wall (thickest, shrinks lumen), lumen

lignification

cell wall thickening

cell death

protoplast breaks down causing empty lumen; dead cells continue to function (structural support, fluid conduction)

xylem than phloem

trees produce more

polymers

macromolecules, made of monomers; structure determines properties

polysaccharides

carbohydrates, cellulose and hemicellulose

phenolic polymers

have benzene ring, lignin

cellulose

long chain, linear; neighboring chains aggregate with hydrogen bonds into 3D structures

hemicellulose

shorter chains, branched; composed of various monomers therefore many varieties, differ between hardwoods and softwoods (greater population in hardwood)

hollocellulose

cellulose and hemicellulose

lignin

very complex, stable but difficult to isolate; made of phenyl-propane, greater population in softwood

cellulose

tensile strength?

lignin

rigidity?

binding everything together?

hemicellulose

extractives

organic compounds, can be extracted with solvents, hardwoods mainly; nonstructural, deter insects and enhance durability

main chemical components of food

cellulose, hemicellulose, lignin, extractives, ash

microfibrils

cellulose chains linked by hydrogen bonds form fibers

lamellae

aggregated microfibrils, embedded in a lignin-hemicellulose matrix; layers form cell walls

concrete analogy

cellulose is rebar, hemicellulose/lignin is concrete

cell wall layers

middle lamellae, primary wall, secondary wall (s1, s2, s3), lumen

middle lamellae

mostly lignin; region between cells

compound middle lamellae

primary wall + middle lamellae + primary wall

primary wall

microfibrils loosely ordered, thin; cell division and enlargement

S1

microfibrils highly ordered, angle nearly horizontal, thin

S2

microfibrils highly ordered, nearly parallel to axis, thickest

S3

microfibrils highly ordered, similar to s1 in organization; relatively thin

pit

hole in s2; usually in pairs (simple, bordered, half-bordered), if not considered blind

aspirated pit

situation in which membrane is pushed against border, blocking pit (water has to be continuous, no air bubbles)

perforation plate

hole in cell wall between two vessels without membrane (simple or scalariform)

spiral thickenings

aka helical thickenings; localized, spiral ridges on inside the secondary wall in longitudinal tracheids

dentation

localized thickenings appearing 'toothlike'; in dentate ray tracheids (stalactites or stalagmites)

2 types of softwood cells

tracheids and parenchyma

4 types of hardwood cells

vessel elements, fibers, parenchyma, and tracheids

softwood cells

longitudinal tracheids, strand tracheids, longitudinal (axial) parenchyma, longitudinal (axial) epithelial cells, ray tracheids, ray parenchyma, radial (horizontal) epithelial cells

softwood tracheids

vertical fluid transport and structural support, dead at maturity; thick cells walls and bordered pits

majority lignin

tracheids are

softwood parenchyma

horizontal food and fluid transport, food storage, extractive production; alive in sapwood only, thin cell walls and simple pits

softwood longitudinal tracheids

most frequent, long and tapered with interlocking fingers; bordered pits with torus to prevent embolism (thin walls big lumen in EW, thick walls small lumen in LW)

softwood strand tracheids

rare; shorter than axial tracheids, square ends stacked in strands, bordered pits

softwood longtudinal parenchyma

appear dark when stained under microscope, simple pits (diffuse, marginal, zonate)

marginal parenchyms

associated with growth rings

diffuse parenchyma

not organized or associated with anything, random

zonate parenchyma

grouped together inside a growth ring

softwood longitudinal epithelial cells

specialized parenchyma; line inside of resin canals and secrete resin

softwood ray tracheids

smaller and shorter than longitudinal variety, ends blunt; commonly on top and bottom of ray rows, bordered pits (can be absent in certain genus)

softwood ray parenchyma

connected to each other by simple pits, connected to tracheids with half-bordered pits; connected to axial tracheids with crossfields (primary cell type in rays)

softwood radial epithelial cells

specialized parenchyma; line inside of horizontal resin canals, embedded inside fusiform rays

resin canals

only in softwoods, vertical or horizontal canals can occur; present/absent, size, frequency, solitary/tangential grouping (traumatic canals can appear in non-usual species in event of injury

even grain

less distinct EL/LW contrast

uneven grain

distinct EW/LW contrast

growth rings

EW to LW transition gradual or abrupt; ring frequency, width of EW to LW

coarse longitudinal tracheids

large diameter, visible with hand lense

fine longitudinal tracheids

small diameter, not visible with hand lense

macroscopic features of softwoods

resin canals, growth rings, longitudinal tracheids, rays, crossfield pitting, longitudinal parenchyma

softwood tangential ray characteristics

height, fusiform, seriation

softwood radial ray characteristics

hetero or homocellular, smooth or dentate, crossfield pitting

types of crossfield pitting

fenestriform, pinoid, piceoid, cupressoid, taxodiod

softwood longitudinal parenchyma characteristics

present or absent, with or without nodules

density

oven dry mass / volume at MC (12% in Hoadley); kg/m^3, g/cm^3, lb/ft^3

specific gravity

ratio of density of wood to the density of water, unitless

vessel elements

vertical fluid transport; dead at maturity, thin cell walls, mostly bordered pits with perforation plates at ends

fibers

structural support; dead at maturity, thick cell walls, simple or bordered pits, shorter than softwood tracheids

hardwood parenchyma

food storage, food and fluid horizontal transport, extractive production, tylosis locale' dead at maturity, thick cell walls, simple or bordered pits

hardwood tracheids

vertical fluid transport; dead at maturity, thin cell wall, bordered pits (not found in all species)

vessel element characteristics

specialized for efficient water conduction, large diameter and lumen, stacked to form vessels, perforation plates

two types of perforation plates in vessels

simple and scalariform

tyloses

balloon-like outgrowths of parenchyma cells that form in heartwood; filled with gums, tannins, and oils

fiber tracheids

bordered pits

libriform tracheids

slit-like simple pits

strand parenchyma

stacked, roughly the same size (like sausage links)

fusiform parenchyma

spindle shaped, no segments

vasicentric tracheid

beside vessel elements, more resistant to embolism than vessels; covered in bordered pits

vascular tracheids

looks similar to small vessel elements, but have pitted ends; stacked vertically, often with spiral thickenings

two types of ray parenchyma in hardwoods

procumbent and upright