ON THE BEHAVIOR OF HARDWOOD PITS TOWARDS BACTERIA DURING WATER STORAGE

Water-stored hardwood logs have shown a certain resistance of their pit membranes towards bacterial decomposition. Since these membranes can be modified due to parenchymatic wound reactions, the pit behaviour was studied with Betula pendula as a reactive species. Branch segments were either water-stored for four weeks or boiled to inactivate the parenchyma. A third series contained samples with wound reactions due to artificial wounding. To study the influence of these different pretreatments on bacterial action, strains capable to degrade cell wall components or aromatics were used. In the water-stored samples parenchyma cells secreted substances which covered the pit membranes. A bacterial mixture attacked neither the secretion products nor the membranes. In the water-boiled samples with no parenchymatic secretion a mixed culture of the cellulolytic/hemicellulolytic Cellulomonas flavigena and the pectinolytic Erwinia carotovora decomposed the pit membranes. The secretion substances of the prewounded samples were partially degraded by a mixture of aromatics-attacking bacteria.