Physical implication of formation of S2L layer in cell wall of gymnosperm compression wood

2022 Fiscal Year Final Research Report

• Project/Area Number: 19H03016
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 40020:Wood science-related
• Research Institution: Nagoya University
• Principal Investigator: Yamamoto Hiroyuki 名古屋大学, 生命農学研究科, 教授 (50210555)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 圧縮あて材 / 針葉樹 / 仮道管 / 細胞壁 / 成長応力 / 二次細胞壁 / リグニン / ミクロフィブリル傾角

Outline of Final Research Achievements

When a green compression wood specimen (CW) is heated in water, it elongates significantly along the fiber direction, while it contracts significantly when dried. A normal wood specimen (NW), on the other hand, shows almost no dimensional chenge.There is a "60-year-old theory", explaining that behaviors peculier to the CW are due to a significant increase in the microfibril angle (MFA) of the S2 layer up to 40-50°.
Furthermore, in juvenile wood (JW), the MFA can be as large as CW. If "established theory" is correct, then behavior similar to CW should be observed also in JW. In the present study, this was empirically verified, and results were negative, strongly suggesting that the CW-specific behaviors are controled not by a high MFA of the S2 layer but by formation of the S2L layer that is located on the outer edge of the CW S2 layer.

Free Research Field

木質科学

Academic Significance and Societal Importance of the Research Achievements

木質部材中に圧縮あて材(CW)が含まれると不規則な寸法変化を生じるため、建材工業ではCWは厳密に避けられる。しかしながら木材工業の原材料は、天然林資源（優良な大径個体）から植林資源（小径丸太）へと急激にシフトしつつある。そのために、CWに起因する加工・利用障害が懸念される。
CWと未成熟材(JW)は、ともに大きなMFAを有するという特徴があり、そのため、物性面でも(いまだに)混同されるきらいがある。本研究では、実証データに基づいて相違点を確認し、その仕組みを細胞壁構造の違いによって明らかにした。驚くべきことに60年来の仮説である“補強マトリックス理論”の見直しが迫られることになった。