Distribution of lignin, pectins and hemicelluloses in tension wood fibers of European ash (Fraxinus excelsior)
Distribution of lignin, pectins and hemicelluloses in tension wood fibers of European ash (Fraxinus excelsior)
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DOI：
10.1163/22941932-40190252
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发表时间：
2019-11-01
期刊：
影响因子：
1.9
通讯作者：
Daniel, Geoffrey
中科院分区：
文献类型：
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作者：
Kim, Jong Sik;Daniel, Geoffrey
尽管关于由S-1+S-2+G细胞壁结构（杨树）组成的拉伸木（TW）纤维中凝胶（G）层的化学性质有相当多的资料，但对由S-1+G结构组成的TW纤维中G层的化学性质知之甚少。本研究采用组织化学和免疫组织化学方法，研究了木质素和非纤维素多糖在白蜡木TW纤维（S-1+G）中的分布。研究的TW纤维完全发育（成熟纤维），并从两个（TW-1，TW-2）成熟的欧洲白蜡树（Fraxinus excelsior L.）。基于微纤丝角（MFA）和所用TW树的差异，TW纤维主要分为三种类型：1）在TW-1中发现的MFA几乎平行于纤维轴的1型纤维，2）在TW-1的生长环末端丰富的具有12度MFA的2型纤维和3）在TW-2中发现的具有10度MFA的3型纤维。所有TW纤维均无S-3层。本文将1型和2/3型纤维的次生细胞壁结构分别定义为G层和GL层。在G/GL层中检测到带有丁香基（S）单元的木质素，其中木质素染色的强度和模式可能与G层和GL层之间MFA的差异有关。与半纤维素，杂木聚糖和杂甘露聚糖表位检测G/GL-层，但这些都比那些在S-2层的正常木材（NW）纤维丰富得多。与木质素一样，G/GL层中的杂甘露聚糖表位的分布模式可能与纤维类型之间的MFA差异有关。在G/GL层中也检测到稀疏的木葡聚糖表位。G/GL层中不存在同型半乳糖醛酸聚糖表位。所有纤维类型在G/GL-层中显示丰富的α-1，5-阿拉伯聚糖表位。总体结果表明，所研究的灰分TW纤维的化学性质与以前报道的其他物种，特别是由S-1+S-2+G结构组成的TW纤维的化学性质显著不同。
Although there is considerable information on the chemistry of gelatinous (G) layers in tension wood (TW) fibers consisting of S-1+S-2+G cell wall structure (poplar), little is known on the chemistry of G-layers in TW fibers organized with S-1+G structure. This study investigated the distribution of lignin and noncellulosic polysaccharides in ash TW fibers (S-1+G) using histochemistry and immunolocalization methods. TW fibers studied were fully developed (mature fibers) and obtained from two (TW-1, TW-2) mature European ash trees (Fraxinus excelsior L.). Based on differences in microfibril angle (MFA) and TW trees used, TW fibers were mainly classified into three types; 1) Type-1 fibers with MFA almost parallel to the fiber axis that were found in TW-1, 2) Type-2 fibers with 12 degrees MFA that were abundant at the end of growth rings of TW-1 and 3) Type-3 fibers with 10 degrees MFA that were found in TW-2. The S-3 layer was absent in all TW fibers. In this study, the secondary cell wall structure of Type-1 and Type-2/Type-3 fibers were defined as G and GL (gelatinous-like) layers, respec-tively. Lignin with syringyl (S) units was detected in G/GL-layers, in which intensity and patterns of lignin staining likely related to the difference in MFA between G- and GL-layers. With hemicelluloses, heteroxylan and heteromannan epitopes were detected in G/GL-layers but these were much less abundant than those in S-2 layers of normal wood (NW) fibers. Like lignin, distribution patterns of heteromannan epitopes in G/GL-layers likely related to differences in MFA between fiber types. Sparse xyloglucan epitopes were also detected in G/GL-layers. Homogalacturonan epitopes were absent in G/GL-layers. All fiber types showed abundant a-1,5-arabinan epitopes in G/GL-layers. Overall results indicate that the chemistry of ash TW fibers studied differs significantly from that of other species reported previously, specifically TW fibers composed of S-1+S-2+G structure.