6 Wood Discoloration

126 6 Wood Discoloration
Fig.6.3. Blue stain in wood. A Artificial bluing of pine boards by Phoma exigua. B Detail.
C Thick, brown hyphae of P. exigua. D Chlamydospores (photo G. Koch). E Perithecia (A,
B, C, E from Schmidt and Huckfeldt 2005), — 5 cm, --- 5 mm
pits (thin hyphae through the margo) and grow there from cell to cell through
the pits. Because fungi colonize the sapwood tracheids and fibers, components
of the capillary liquid also might be used as nutrients. Although there are
special microhyphae, transpressoria (Fig. 2.5), which can break through the
wood cell wall, probably by physical pressure and/or enzymatic action (Schmid
and Liese 1966; Liese 1970), in most cases the strength properties of wood are
hardly affected. Thus, the occasionally used term “blue rot” is wrong. Some
species however caused some strength loss. Toughness was the property most
seriously affected (Seifert 1999; Schirp et al. 2003b). In most cases, however,
the damage to wood is mainly cosmetic. The damage however affects domestic
and export earnings for the forest industries. For example, Pinus radiata in
New Zealand is highly susceptible to blue stain with an estimated annual loss
in revenue of NZ$ 100 million per year (Thwaites et al. 2004).
Temperature minimum depends on the species, and is between 0 and −3 ◦ C;
the optimum is between 18 and 29 ◦ C and the maximum is between 28 and
www.taq.ir