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Wollemi Pine research - wood anatomy
Using samples from the trunk collected by the NSW National Parks and Wildlife Service rangers (see age and ancestry) we have been able to examine the anatomy of the wood. An electron scanning microscope was used to produce these images on the right, which are explained below.
Figure 1 An oblique view of the corner of a small block of the wood of Wollemi Pine. The scale bar indicates 0.5 mm. Transverse and tangential surfaces, and their structural inter-relationships can be seen. Approximately 90% of the wood consists of tracheids, 9% is ray and 1% axial parenchyma cells. This is typical of other conifer woods. In the transverse plane (upper half of image) the cut ends of tracheids are visible (figure 2 shows a magnified version). The two lines extending obliquely from above and below the upper left corner are growth rings (figure 3 shows a close-up view of a growth ring). The lower right of the image shows wood in the radial longitudinal plane with tracheids aligned axially and rays aligned radially. A higher magnification view of this plane is shown in figure 4. In the tangential longitudinal plane (lower left of image) the cut ends of rays can be seen (see also figure 5).
Figure 2 Magnified view of the cut ends of two tracheids as seen in transverse section. The tracheids are hollow tubes approximately 0.02 mm wide and 3 mm in length. Bordered pits, which interconnect tracheids, can be seen inside the uppermost tracheid. The scale bar indicates 0.01 mm.
Figure 3 Magnified view of part of a growth ring. The scale bar indicates 0.05 mm. The smaller (latewood) cells (on the right side of the image) were produced in the winter and the larger (earlywood) cells (on the left) were formed in the spring. The long cells, one extending the full width of the image just below centre, and the other in the lower left of the image are the cut sections of rays.
Figure 4 Radial longitudinal surface showing a ray, four cells high, aligned horizontally. Tracheids are aligned vertically. On the right side of the image the ray has been cut through radially, exposing its interior. The numerous perforations (on the left) and circular indentations (on the left) of the ray surface are cross-field pits that interconnect ray cells with tracheids. The scale bar indicates 0.1 mm.
Figure 5 Tangential longitudinal surface showing the cut ends of rays. In this image they range from two to twelve cells in height. The tracheids, which have been cut longitudinally, are aligned vertically in the image. Rows of circular-shaped bordered pits line the tangential walls of some of the tracheids. The scale bar indicates 0.02 mm.
Dr Roger Heady (Australian National University, visiting Researcher)