会议名称：“2022世界木材日”研讨会暨第四届国际林联（IUFRO）林产品文化研究组讨论会
会议时间：2022年3月21日

报告嘉宾：David Collings
嘉宾简介：澳大利亚西澳大学荣誉研究员

摘要：

Interlocked and spiral grain are examples of wood grain that run in non-vertical orientations. The developmental mechanisms that generate these grain patterns likely involve the slow rotation of fusiform initials within the vascular cambium, but how these mechanisms function at a cellular level remains unclear. Clarification of these developmental pathways may come through assessing grain at the cellular level across large areas of wood, but such experiments are difficult using traditional serial sectioning. To overcome these limitations, wood samples were assessed by X-ray computed microtomography (µCT) with the Skyscan 1172 system. µCT generates large data sets at near cellular resolution that can be resliced and reoriented in ImageJ. Furthermore, reconstructed tangential longitudinal 77sections processed through the DIRECTIONALITY plug-in, which uses a Fast Fourier Transform to measure dominant alignments within an image, give direct measurements of wood grain. We demonstrated µCT’s applicability to grain measurements in multiple systems. African mahogany (Khaya) exhibits interlocked grain with grain oscillations of more than 20o measured with µCT. Grain changed at locally constant rates separated by locations where grain change abruptly reversed. Image segmentation of cross sections identified vessels whose orientations were more variable than fibres, and which typically deviated further from vertical at locations where grain change reversed. Moreover, reversal locations for vessels were shifted ~400 µm towards the pith compared to the fibres. A model is proposed to explain interlocked grain development and the origin of these differences. Additionally, µCT demonstrated links between compression wood formation and spiral grain development in 8 month-old radiata pine saplings.
The normal development of progressively steeper left-handed spiral grain in vertically grown trees was inhibited by the formation of compression wood on the lower sides of tilted trees. These results demonstrate a previously unidentified link exists between compression wood formation and the inhibition of spiral grain development.

责任编辑：iwcs2233H