Zones of Gelatinous Fibers in Populus Balsamifera L.

David C. Ritter, Robert E. Kroll, Roland O. Gertjejansen

Abstract


Although balsam poplar (Populus balsamifera L.) is a logical supplement to the aspen (Fopulus tremuloides Michx.) resource for the manufacture of oriented strandboard (OSB), it has not been utilized extensively because of reported machining problems. The machining difficulties usually have been attributed to fibers with thick gelatinous layers in their cell walls. This study employed scanning electron microscopy (SEM) to observe the cell-wall structure of balsam poplar grown in Minnesota. In a previous study, balsam poplar samples were identified as difficult to waferize on the basis of wood fibers plugging the waferizing knives. The balsam poplar samples that were difficult to waferize often contained areas that appeared as "white rings" to the naked eye. Observation with the scanning electron microscope revealed that the "white rings" in the wood were zones that contained very high concentrations of gelatinous fibers. In these fibers, the cell wall typically consisted of a gelatinous layer that occupied 30 to 90% of the cell wall. In most cases, the initiation and termination of zones with high concentrations of gelatinous fibers took place within one annual growth increment or slightly more. Additional observation of trees within the sample showed that the "white rings" and the accompanying high concentrations of gelatinous layers were usually restricted to one side of the tree. This observation has led us to believe that the "white ring" areas and the corresponding zones of gelatinous fibers were the result of tension wood formation in the balsam poplar trees and not a part of normal wood formation.

Keywords


Balsam poplar;gelatinous layer;G-layer;gelatinous fiber;machining;oriented strandboard;scanning electron microscopy;tension wood;waferizing

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