Biomodification ofPinus radiatawood to enhance penetrability
2009
Singh, Adya P. | Schmitt, Uwe | Dawson, Bernard S. W. | Rickard, Catherine
Pits form a major pathway for liquid flow in wood. In conifers, such as radiata pine (Pinus radiata D.Don), pits between axial tracheids are highly specialised structures, with cell walls overarching a membrane. The membrane consists of a central impervious torus, which is suspended in the pit cavity by a highly porous margo. The bordered pits in radiata pine become aspirated during drying of timber, a condition where the torus becomes lodged against the pit aperture and seals it, thus influencing timber permeability/penetrability. To enhance timber treatability we have employed an environmentally compatible biological process to remove pit membranes, thus facilitating greater flow of applied wood property enhancing solutions through pits. The biological modification process we employed involved placing freshly sawn radiata pine boards in water in plastic troughs in a glasshouse, and keeping them submerged for periods sufficient for the natural bacterial microflora to colonise wood and destroy pit membranes. - The boards were removed from the troughs after 2-12 weeks and examined by a range of microscopy techniques, including fluorescence confocal microscopy, field emission scanning electron microscopy and transmission electron microscopy, which provided evidence of bacterial colonisation of pit membranes and pit membrane destruction. The microscopic assessment of wood permeability indicated that penetration depth of applied coating was significantly greater in the ponded wood compared with the unponded (control) wood. A fruitful extension of the work presented here would be to develop a biological pre-treatment process using enzymes that will specifically target pit membranes and can be produced cost-effectively for industrial scale operations.
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