Hiroki Sakagami, Junji Matsumura and Kazuyuki Oda

Confocal laser scanning microscopy (CLSM) was applied as a new method of visualizing the shrinkage of wood and its anisotropy. Control of relative humidity and temperature in a specialized environment chamber made it possible to acquire transverse images of tracheids of Akamatsu (Pinus densiflora) from the saturated condition to the dried condition. The shrinkage of tracheid cells was also determined by measuring the tangential diameter of tracheid and lumen, the radial diameter of tracheid and lumen, and the thickness of tangential and radial walls. Moreover, this technique makes it possible to discuss the relationship between moisture content and tracheid cell shape. We found the CLSM technique to be an effective method for visualizing shrinkage of tracheid cells with desorption.

Hiroshi Matsunaga, Junji Matsumura and Kazuyuki Oda

The objective of this study was to understand the micro-distribution of a copper-based preservative in wood in connection with anatomical morphology and to consider the fixation of copper in wood. Bulk specimens and semi-ultra thin sections (0.5 μm) obtained from Japanese cedar (Cryptomeria japonica) were treated with a CuAz preservative solution. After fixation of the solution in wood components, SEM-EDXA (Scanning Electron Microscope equipped with an Energy Dispersive X-ray Analyzer) was used to investigate the micro-distribution of copper. The use of semi-ultra thin sections improved characteristic X-ray spatial resolution and made it possible to analyze the micro-distribution of copper. In both earlywood and latewood of the sapwood, copper was more abundant in the compound middle lamella than in the secondary wall and concentrated in the tori. Copper was most concentrated as crystalline deposits in longitudinal parecnhyma cells. Semi-quantitative analysis revealed the copper amount to increase in this order: secondary wall in tracheids < middle lamellae < membrane of half-bordered pits < tori in tracheid pits < deposits in longitudinal parenchyma cells. These different concentrations may indicate significant interactions between the amine-copper complex in CuAz and chemical constituents of wood.

Felix Dalitso Kamala, Hiroki Sakagami, Kazuyuki Oda and Junji Matsumura

Growth ring structure and wood density were compared among five families of Pinus patula planted in Malawi, Africa. The vertical and radial variations of wood density and growth characteristics were investigated in stems of 30-year-old Pinus patula planted at a spacing of 2.74 × 2.74 m. The pattern of ring width with cambial aging was broadly similar at all stem heights: wide to the 4th growth ring, decreasing gradually up to the 10th ring and then very narrow towards the bark. In all the families, the first complete growth ring was the widest, ranging from 20 to 50 mm across the families. This trend was different from other similar studies carried out in Zimbabwe and South Africa where the growth ring width increased from the 1st to the 3rd ring with the highest ring width of 19 mm. Specific gravity varied with height above the ground for all the trees. The average specific gravity was 0.56. Weak to medium correlations between latewood percentage and specific gravity were observed. The study shows that selection for density in Pinus patula could be made at least by the age of 10 years.

Shinya Koga, Kazuyuki Oda, Juichi Tsutsumi and Takaaki Fujimoto

The objective of this study was to determine the effect of thinning on the annual ring structure and the cross-sectional dimensions of tracheids in plantation-grown Japanese larch (Larix leptolepis). Annual ring width, earlywood width and latewood width increased significantly after thinning. The width of the band of nonflat latewood tracheids in the annual ring increased more than that of flat latewood tracheids. Thinning did not significantly affect latewood percentage. The average radial diameter of both earlywood and latewood tracheids increased after thinning. After thinning, average wall thickness of earlywood tracheids increased, while that of latewood tracheids decreased. Cell wall percentage in earlywood was not influenced significantly by thinning, but latewood cell wall percentage decreased. The changes of the average radial tracheid diameter, the average wall thickness of tracheids and cell wall percentage from earlywood to latewood within a growth ring became more gradual after thinning. However, thinning did not affect significantly the cell wall percentage of the whole growth ring. This study suggests that thinning has little effect on wood density of the whole growth ring in Japanese larch.

Hiroki Sakagami, Kosuke Tsuda, Junji Matsumura and Kazuyuki Oda

The microcracks occurring during drying of wood were visualized under confocal laser scanning microscopy (CLSM). Precise control of relative humidity and temperature in a specialized environment chamber made it possible to acquire sequential images of the wood of Cryptomeria japonica during drying from the water-saturated condition. The images indicated that the microcracks occurred between tracheid and ray parenchyma in the latewood region and the crack tip advanced in both the bark and pith directions. Subsequently, the crack tip expanding towards the bark stopped at the earlywood region through the growth ring boundary. The other tip toward the pith stopped at the earlywood region before reaching the growth ring boundary. Our technique made it possible to generate microcracks and discuss the relationship between moisture content and microcrack formation during drying. We found the CLSM technique to be an effective method for visualizing microcrack propagation with time.

Toshihiro Umebayashi, Yasuhiro Utsumi, Shinya Koga, Susumu Inoue, Seizo Fujikawa, Keita Arakawa, Junji Matsumura and Kazuyuki Oda

The interspecific variation of dye ascent in the stems of 44 broadleaved deciduous species growing in Japan was studied using freeze-dried samples after dye injection. The dye ascending pattern differed both within and between ring-porous and diffuse-porous species. In large earlywood vessels of all ring-porous species, the dye ascended only in the outermost annual ring, and the inner annual rings had lost their water transport function. The dye ascending pattern within the inner annual rings in the ring-porous species was categorized into three types: i) the dye ascended both in the many latewood vessels throughout the latewood and small earlywood vessels; ii) the dye ascended in the many vessels throughout the latewood; and iii) the dye ascended mainly in the late latewood vessels. In diffuse-porous species, the dye ascending pattern within the annual rings also was categorized into three types: i) the dye ascended throughout the annual rings; ii) the dye ascended mainly in the earlywood vessels; and iii) the dye ascended mainly in the latewood vessels. Xylem water distribution was also examined by cryo-SEM in three ring-porous and three diffuse-porous species that had different dye ascending patterns. The water distribution pattern within annual rings was correlated with the dye ascending pattern except for one diffuseporous species (Salix gracilistyla). In this case, water was distributed in the whole region of the annual rings although dye was mainly distributed in the earlywood. These results showed that the functional area of water transport within annual rings differed among ring-porous species and diffuse-porous species.