A PROPOSED MODEL OF THE TRACHEID CELL-WALL OF SOUTHERN YELLOW PINE HAVING AN INHERENT RADIAL STRUCTURE IN THE S-2 LAYER

During our many SEM studies on brown-rot decayed or oxalic acid-treate d wood blocks, our observations consistently showed that the St layer of degraded tracheid cell walls possessed an underlying structural con figuration perpendicular to the lamellae. We hypothesized that fungal decay and/or acid attack had revealed, rather than modified, the under lying wood chemical composition and ultrastructure which is not eviden t in undecayed wood. From this we conclude that there are radial plane s of low molecular-weight hemicellulose across the St layer, in additi on to the previously recognized concentric layering of cellulosic micr ofibrils. These radial planes of hemicellulose can be exploited by aci d-mediated fungal and thermochemical agents that reveal the radial ult rastructural organization in degraded cell wall remnants.