毛果冷杉湿心材的闭塞纹孔及细菌对木材结构的降解

扫描电镜观察到毛果冷杉湿心材部位管胞具缘纹孔纹孔膜上存在着水痕状、片状或块状的细菌,而在正常材部位没有发现。细菌的活动不但使湿心材部位的部分射线薄壁细胞发生降解,而且纹孔膜塞缘的微纤丝束也偶尔被降解而产生断裂。生材时,湿心材管胞间的具缘纹孔纹孔膜严重结壳并闭塞,早、晚材管胞具缘纹孔的闭塞率分别为77.7%和72.1%,而正常材大多数是非闭塞的,早、晚材的闭塞程度分别只有6.8%和13.4%。湿心材中存在的大量闭塞纹孔,是导致木材干燥困难的主要原因。

Aspirated Pits in Wetwood and Micromorphology of Microbial Degradation of Sub-alpine Fir

Differentiating from normal wood,bacterial of water drop shape,flake shape and lump shape are observed in pit membrane in wetwood of Abies lasiocarjpa(Hook) Nutt.(sub-alpine fir) using scanning electronic microscope.Not only ray parenchyma cells in wetwood are partially degraded but also margo strands in pit membranes are somewhat degraded by bacterial activities.Most of bordered-pit membranes in normal wood are un-aspirated at green condition and the proportions of aspirated pits in early wood and latewood are only 6.8% and 13.4% respectively.Nevertheless,most of bordered-pit membranes in wetwood are aspirated at green condition and the proportions of aspirated pits in early wood and latewood are at 77.7% and 72.1% respectively.The problem of hard-to-dry for sub-alpine fir could be reasoned from the considerable amount of aspirated pit membranes in wetwood.