1 / 13

Reaction Wood

Reaction Wood. Reaction wood is formed as a response by the tree to a triggering event such as tipping from the vertical. It is also known to regulate the orientation or angle of branches relative to the main stem. (Haygreen & Bowyer).

raymond-kemp
Download Presentation

Reaction Wood

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Reaction Wood Reaction wood is formed as a response by the tree to a triggering event such as tipping from the vertical. It is also known to regulate the orientation or angle of branches relative to the main stem (Haygreen & Bowyer)

  2. The terminology used to describe reaction wood formed in softwoods and hardwoods comes from the stresses normally present in those locations. However, those stresses themselves are NOT responsible for the formation of reaction wood. (Haygreen & Bowyer)

  3. Compression wood – macroscopic appearance Compression wood (Hoadley)

  4. Compression wood – microscopic appearance Light microscope Transmission electronmicroscope Scanning electronmicroscope

  5. Ultrastructure of longitudinal tracheids (Josza)

  6. Compression wood – microscopic appearance Compression wood Compression wood Normal wood

  7. Anatomy Wider growth rings More latewood Shorter longitudinal tracheids Rounded cells with intercellular spaces Helical striations (following S2Ө) Ultrastructure Larger S2Ө S3 absent New S1L layer Chemistry More lignin Less cellulose Hemicelluloses differ Properties Higher wood density Compression strength ↑ All other strengths ↓ Brittle failure Greater longitudinal shrinkage Lower pulp yields * Compression wood – characteristics and properties

  8. Tension wood – macroscopic appearance Tensionwood (Hoadley)

  9. Tension wood – microscopic appearance (Hoadley) G-layer Aspen normal wood Aspen tension wood

  10. Tension wood – appearance of G layer Microfibril orientation

  11. Anatomy Fibers affected not vessel elements Gelatinous fibers (G-layer) Ultrastructure SG - after S3 - replaces S3 - replaces S2 + S3 - replaces some of S1 + S2 + S3 Microfibrils less closely packed Low Ө in G-layer Higher S1Ө Chemistry More cellulose Less lignin Hemicelluloses differ Properties Higher wood density Compression strength ↓ Seasoning defects Higher pulp yields Poor workability (“fuzzy” grain) * Tension wood – characteristics and properties

  12. Location of reaction wood formation Compression wood formation in horizontally oriented stem. Compression wood is found on underside of stem – not on side of stem under compression. (Haygreen & Bowyer)

  13. Location of reaction wood formation Reaction wood formation in growing looped stem. Compression wood is found consistently on underside of stem and tension wood is found consistently on upper side of stem (regardless of the nature of the stresses experienced in those locations). a. Softwood b. Hardwood (Haygreen & Bowyer)

More Related