材質育種にむけてのスギ品種の年輪構造

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三倍体を含むスギ品種を対象に,品種に特有な年輪構造に関係する形質を明らかにし,さらに特有な形質と木材の性質との関係を検討することを目的として,年輪構造の観察と縦圧縮試験とを行った.仮道管の接線壁の厚さ,壁率には品種間に大差が認められなかったが,晩材率,容積密度数,仮道管長および仮道管径は品種によって異なっている｡特に,三倍体品種では,二倍体品種に比べて仮道管が長く,しかも仮道管および放射柔細胞の直径が大きく,木部細胞が巨大化する傾向がある.一方,晩材率が大きい品種ほど容積密度数が増大し,品種間の容積密度数の違いは晩材率の差異によって生じる.比重は圧縮強さおよび圧縮破壊仕事量との間に正の相関関係を持っている.晩材仮道管長は,圧縮ヤング率との間に正の相関関係があるものの,圧縮破壊ひずみおよび圧縮破壊仕事量との間に負の相関関係を示す.また,晩材ミクロフィブリル傾角は晩材仮道管長および圧縮ヤング率との間に負の相関関係を持ち,圧縮破壊ひずみおよび圧縮破壊仕事量とは正の相関関係にある.このために,圧縮ヤング率と圧縮破壊ひずみとの間,および圧縮ヤング率と圧縮破壊仕事量との間には,晩材ミクロフィブリル傾角を介してそれぞれで負の相関関係が存在している.比重,晩材仮道管長,および娩材ミクロフィブリル傾角に品種間の違いがあるとき,縦圧縮に対する力学的性質を検討した.その結果,スギ品種は,①圧縮ヤング率は高いが低い強さと小さな破壊ひずみを示すタイプ,②圧縮ヤング率は低いが高い強さと大きな破壊ひずみを示すタイプ,③これらの中間を示すタイプに大別された.Annual ring structures and compressive properties of sugi cultivars were investigated. Three trees each from five cultivars and two trees each from four other cultivars including two triploid cultivars were felled in a 25-year-old stand and a 30-year-old stand, respectively. About 10 cm thick disk was taken from the breast height of each tree stem and was dried at room temperature. Annual ring structures of the disks were examined on nine cultivars and compression tests parallel to the grain of mature wood were done on seven cultivars. Ring structures of the pieces were also analyzed after compression tests. The results obtained may be summarized as follows: 1) There were no significant differences in tangential wall thickness and cell wall percentage of tracheid among the cultivars, but latewood percentage, basic density, tracheid length and tracheid diameter depended on cultivars. Tracheid length was longer and the diameters of tracheid and ray cell were larger in the triploid cultivars than in the diploid cultivars. 2) The cultivars having high latewood percentage showed large basic density, and high correlation between latewood percentage and basic density was obtained as a whole. 3) Specific gravity was correlated positively with compressive strength and also with work to maximum load, Latewood-tracheid length was correlated positively with Young's modulus, negatively with strain at maximum load and negatively with work to maximum load. Latewood-microfibril angle was also correlated positively with strain at maximum load and with work to maximum load, and negatively with Young's modulus. Therefore negative correlations were found between Young's modulus and strain at maximum load and between Young's modulus and work to maximum load. 4) Due to the differences in specific gravity, latewood-tracheid length and latewood-microfibril angle among the cultivars, the compressive properties depended on cultivars. The examined cultivars were roughly classified into three groups on terms of the compressive properties: Type 1 has higher Young's modulus, lower compressive strength and smaller strain at maximum load, Type 2 has lower Young's modulus, higher compressive strength and larger strain at maximum load, and Type 3 has intermediate values between Type 1 and Type 2.
九州大学の論文

材質育種にむけてのスギ品種の年輪構造

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