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Wood Chemistry PSE 406

Wood Chemistry PSE 406. Tree & Wood Structure. Agenda. Tree components Stem, crown, roots Hardwood versus softwood Macro wood structure Reaction wood Micro wood structure Cell types Cell wall layers. Why Wood Structure?.

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Wood Chemistry PSE 406

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  1. Wood ChemistryPSE 406 Tree & Wood Structure

  2. Agenda • Tree components • Stem, crown, roots • Hardwood versus softwood • Macro wood structure • Reaction wood • Micro wood structure • Cell types • Cell wall layers

  3. Why Wood Structure? • Chemical distribution is dependent upon macro and microscopic structure. • Tree species dependent • Dependent upon position in tree • Cell type dependent • Dependent upon position in the cell

  4. Tree Structure I • It has been my experience that the majority of students taking wood chemistry can’t tell the difference between a hardwood and a softwood. In the next few slides I am going to present you with the layman's view of what is a tree

  5. Tree Structure II • In general, trees contain these structural components: • Stump/Roots • Stem (wood & bark) • Crown: live/dead branches, foliage (leaves/needles), flowers and fruits. • There are major chemical components which are found in all of these components. We will focus on the components found in the stem.

  6. Hardwoods Trees containing leafs Typically lose foliage in winter Maple, alder, oak, Softwoods Trees containing needles Typically retains needles over winter. Pines, firs, cedars, spruce Tree Structure III

  7. Tree Species Differences

  8. Tree Composition 1. Values for branches, foliage, bark, and wood = % of tree above ground 2. Values for roots is a separate measurement = % of total tree

  9. Macroscopic Structure Annual Rings Outer Bark Phloem (inner bark) Pith Cambium Xylem Heartwood Earlywood Knot Sapwood Definitions in notes section Latewood

  10. Reaction Wood This is a very poor representation of a very bent tree Tension Wood (Hardwoods) Compression Wood (Softwoods) Tension or Compression Wood Notes

  11. Wood Microscopic Structure • Imagine that wood is made up of millions and millions of toilet paper rolls glued together. These rolls are the fibers that will make paper • Most often the ends of these tubes are sealed. There are small holes in the sides of the tubes to allow water to pass through

  12. Microscopic Structure • Microscopic structure of wood (Textbook of Wood Technology, Panshin, A. J., page 118 Notes

  13. Softwood Cells Source: Wood Chemistry, Fundamentals and Applications. Sjostrom page 7 Hardwood Cells Source: Wood Chemistry, Fundamentals and Applications. Sjostrom page 10 Hardwood & Softwood Fibers

  14. Microscopic Structure • Structure of woody cell by Cote, 1967. This figure is used by almost every wood chemistry text. It can be found in Wood Chemistry, Fundamentals and Applications by Sjostrom on page 14. Notes

  15. Cell Cross Section Primary Secondary 1 Secondary 2 Warty Layer Secondary 3 Middle lamella

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