Wood Flashcards
Softwood
- A type of tissue found in conifers
Hardwood
- Only dicotyledon class of flowering plants
Angiosperm
- Flowering plant
Gymnosperm
- Conifers
- Cone-bearing seed plants
Divisions of trees
- Angiosperms
- Gymnosperms
Classes of Angiosperms
- Dicotyledon (eudicot)
- Monocotyledon
What is wood made from?
- Accumulation of cell walls of the secondary xylem in conifers and dicot flowering plants
What is Xylem and Phloem?
- xylem and phloem are vascular tissue
- Xylem conducts water upwards
- Phloem conducts organic constituents
- Can be secondary or primary
What is secondary growth?
- In diameter of plant (girth)
- Cambium (lateral meristem)
- Produce phloem toward outside of plant, xylem toward inside
- Monocots don’t have secondary growth
What is primary growth?
- Apical
- Produces leaves, non-woody stems, roots
What is the accumulation of xylem tissue?
Wood
Annual ring of xylem is what?
- Formed in one growing season
- Tree rings
- Dendrochronology to get age of tree by annual accumulation of xylem rings
- Springwood cells larger than later season cells
Types of xylem cells
- tracheid cells, long and thin with tapered ends
- Vessel elements, short wide cells, align to form pipe-like vessels
What happens when xylem cells form secondary cell walls?
- Cell walls harden with cell death
- Still work in conduction
What type of xylem cells do conifers mostly have?
- Tracheid
- Makes wood more uniform
What type of xylem cells do angiosperms mostly have?
- Dicots have more of both types
- Makes more variety wood
Where does the property of wood come from?
- Lignification of secondary xylem walls
- Thickening of cell wall by lignin gives hardness
Lignin
- Polymers of lignin subunits, many variations in final structure
- Phenolic compounds
- Up to 40% of plant organic material
- One of the most abundant organic substances in nature
Importance of lignin
- Strengthens around fibrous polysaccharide cell wall
- Allows plant to become large, tall, upright structures
- Evolutionarily, adaptation of form in successful transition from aquatic to terrestrial habitat
Why are there different types of wood?
- Polymerization of phenolic subunits is ‘random’
- Final polymers not uniform in result
- Wood from different sources have different characteristics
What makes wood harder?
- More lignification
- Breakdown of random polymerization of subunits is difficult, makes wood durable
BC temperate rainforest
- Few species of trees but large numbers of each (softwoods)
Tropical rainforest
- Many diverse trees, interspersed (hardwoods)
Where is the main source of hardwood in the world?
- Tropical Asia
Bark
- Phloem and protective covering layer, periderm
- Periderm expands as plant grows in girth
Cork
- Major part of periderm
- Useful for special properties
Special properties of Cork and what is Suberin?
- Air-filled principally dead cells
- cell walls contain suberin,
- Suberin is a Complex polymer of phenolics and long hydrocarbon chains, A Waxy component
- Impermeable, buoyant, elasticity
- No synthetic contains all these properties
What do the special properties of cork do for the plant?
- Physical protection, insulation, and fire protection
What are uses for cork?
- Wine stoppers
- Gaskets
- Badminton shuttlecocks
- Flooring
- Acoustic and thermal insulation
- Bulletin boards
History of paper
- Plant fibres into paper first developed by Chinese, documented in year 105 from bark of mulberry tree
- Didn’t reach Europe for 1000 years
- Paper rare and valuable in history
What is a major product of Canadian forestry?
- Wood pulp paper
Wood pulp paper technology developed when?
- late 19th century
What kind of wood is suitable for paper?
- Conifer, softwood
- Uniform tracheid cells
How is wood pulp paper made?
- Wood stripped of bark and chipped
- Chemical or mechanical process
What is the mechanical process for producing paper?
- Simple grinding
- Slurry washed, screened, and pressed
- Cheap quality, yellow, and degrades
What is the chemical process for producing paper?
- Cook in digester to dissolve lignin
- Harsh acid or alkali treatments to dissolve other components like resins
- Bleaching and texturizing agents for white and quality paper
What are some of the environmental impacts of paper production?
- Uses energy and strong chemicals
- 40-50% of worlds industrial logging is for paper
- Pulp and paper industry responsible for 4% of world energy use
- Polluter of air and water
Has digital documentation and electronic communication resulted in a reduction of paper use?
- No
- But paper going into landfills has been declining since 2000
How much of Canada’s waste does paper account for?
one third
What is the single largest category of paper use?
- Packaging accounts for 41% of all paper used
