Page 382 - Biosystems Engineering

Evaluation of Transgenic Wood for Pr oductivity & Quality 359

genetic modification on trees could improve wood durability, espe-
cially mold resistance.

12.3.5 Advanced Analysis Tools
To efficiently monitor and control the properties of transgenic wood,
rapid and small-scale analytical tools are required. These tools will be
more important when a tree that is just a few months old needs to be
investigated. Several advanced analysis tools, which have been used or
will be used to analyze transgenic wood, will be discussed as follows.

Tree-Ring Machine/SilviScan
In recent years, several developments have taken place in biotechnol-
ogy, including genetic tree improvement. Characterizing wood qual-
ity quickly and reliably becomes more important for evaluating if the
genetic application is successful or not. The recent development of
SilviScan-2 (Evans 1997, 1999) has provided a tool to conduct the
rapid scanning of increment cores for tree improvement programs
and large-scale resource assessments. SilviScan provides pith-to-bark
measurements of fiber width, wood density, and microfibril angle.
From these data, fiber-wall thickness, coarseness, and wood stiffness
can be estimated.
SilviScan is an automated wood-microstructure analyzer devel-
oped for the rapid assessment of wood properties, including wood
density and MFA by a combination of x-ray diffractometry, x-ray
densitometry, and digital microscopy (Evans 1997; Evans and Ilic
2001). Diffraction patterns collected on SilviScan can be integrated
over a specified radial section; thus, pith-to-bark profiles of wood
density and MFA variation can be obtained at different spatial resolu-
tions. Density was scanned at a resolution of 25 μm, whereas MFA
had a resolution of 1 mm.
The elastic modulus of wood specimens can be calculated from
the SilviScan wood density and MFA using the following equation:

E = ( ) B (12.1)
A DI
CV
where A and B are constants calibrated using sonic resonance data. D
(g/cm ) is the scanning wood bulk density, and I is the coefficient of
3
CV
variation of the 002 azimuthal diffraction profile determined by MFA
(Evans 1999).
The Quintek Measurement Systems also developed an instru-
ment to measure increment core tree ring samples. A complete print-
out listing ring counts, ring years from core date, radial growth by
year, early wood and late wood percentage, early wood and late
wood density, ring density, and average core density is generated
from single thin strips. Figure 12.4 shows a density profile of south-
ern pine measured by the x-ray method. The profile shows six tree
rings with detailed earlywood and latewood information.