**6. Acknowledgements**

298 Gamma Radiation

Considering the patterns and mechanisms of decay of white-rot fungi, in the beginning of decay they utilise simple carbohydrates – the ones incurred by gamma radiation. During further incubation, white rot fungi mainly utilise lignin, and they use radical mechanisms to degrade lignin. Broken (somehow modified) lignin accompanied with radicals incurred in wood by gamma radiation could negatively interfere with these decay patterns. Therefore no significant difference in ML caused by white-rot fungi between autoclaved and irradiated

In contrary to white rot, brown rot decay mechanisms, particularly decay mechanism of *P. placenta,* are less radical dependent, higher radiation doses do not influence the decay patterns of this brown rot fungus. In contrast, higher irradiation resulted in higher degree of depolymerisation, what makes wood significantly more susceptible to dacay (Despot *et al.*

Fig. 17. Correlation between Mass loss (ML) of autoclaved and irradiated specimens and

durability of pine wood and needs to be considered for wood durability testing.

increased linearly, while the maximum swelling seems to be unchanged.

However, it has to be taken into consideration that depolymerisation of wood components by gamma irradiation is one aspect that could explain differences in changed "natural"

Gamma radiation at a level of 30 to 150 kGy causes irreversible and permanent changes in chemical and mechanical properties of wood. Using the HEMI test method it was possible to detect small but significant changes in structural integrity and brittleness of wood caused by gamma radiation. With increasing radiation dose the total amount of water-soluble sugars

The method of sterilisation has a considerable influence on the natural durability of pine wood. However, wood sterilisation by gamma radiation has different influence on white

incubation time to fungus: A) *Poria placenta*; B) *Trametes versicolor*.

specimens was determined (Despot *et al.*, 2006; Hasan *et al.* 2006a).

**Resistance against white-rot fungi**

2006, 2007; Figure 17).

**5. Summary** 

Part of the research on the influence of gamma radiation onto wood properties was supported by the COST Action E37 in the frame of a Short-Term Scientific Mission (STSM) awarded to Marin Hasan, PhD. Parts of the experimental work were carried out at the Federal Research Centre for Forestry and Forest Products (BFH), Hamburg, Germany, which was the STSM host institution, and whose hosting is gratefully acknowledged. The authors extend their particular thanks to BFH and to Ruđer Bošković Institute in Zagreb, Croatia for gamma radiation provision and to its scientists for sharing their wide-ranging scientific expertise on gamma radiation.
