Effects of thermo-vacuum treatment on the anatomical structures of Szemao pine wood and alder birch wood
The anatomical structures of both untreated and thermo-vacuum treated (the temperature of 200°C, the duration of 4h and the relative pressure of -0.08 MPa) Szemao pine wood (Pinus kesiya var. langbianensis) and alder birch wood (Betula alnoides) were observated and analysed by light microscopy. The obtained results were as follows. (1) Szemao pine wood with thiner earlywood cell walls and thicker latewood cell walls, which was an abrupt transition from earlywood to latewood, was not susceptible to the thermo-vacuum treatment (TVT) in this test. Only smaller radial cracks were observed in the cross section, and ray parenchyma cells which they were non-lignified cells were partially destroyed. Longitudinal tracheids walls remained intact and were not destroyed. (2) No destruction was also observed except part of the scalarform perforations plates in alder birch wood under the TVT. The results indicated that effects of the TVT on the anatomical structures of woods were slight. In addition, the extractives of both szemao pine wood and alder birch wood were removed, playing an important roles in improving the permeability of wood after the TVT.