Anni M. Harju

Chemical factors affecting the brown-rot decay resistance of Scots pine heartwood

The cell wall chemistry (amount of hemicellulose, α-cellulose, and total lignin) and the concentration of extractives (total acetone-soluble extractives, resin acids, pinosylvins and the total phenolics quantified as tannin acid equivalents) were studied in brown-rot resistant and susceptible juvenile heartwood of Scots pine (Pinus sylvestris L.). The study material consisted of a total of 18 trees from two 34-year-old progeny trials at Korpilahti and Kerimäki. The trees were selected from among 783 trees whose decay rate had previously been screened in a laboratory test using a brown-rot fungus, Coniophora puteana. Samples from neither location showed any significant difference in the concentration (mg/cm3) of hemicellulose, α-cellulose and total lignin between the decay resistant and susceptible trees. At both locations only the concentration of total phenolics was higher in the decay-resistant heartwood than in the decay-susceptible heartwood. At Korpilahti, the amount of acetone-soluble extractives and the concentration of pinosylvin and its derivatives were higher in the resistant than in the susceptible trees.

The concentration of phenolics in brown-rot decay resistant and susceptible Scots pine heartwood

The concentrations of three individual stilbenes, pinosylvin (PS), pinosylvin monomethyl ether (PSM), and pinosylvin dimethyl ether (PSD), and the total concentration of phenolic compounds were determined in 34-year-old Scots pines which were known to have either decay-resistant or susceptible heartwood. The sample trees were selected from two progeny tests among 783 trees; the decay resistance of which had been screened earlier in vitro against a brown-rot fungus Coniophora puteana. Ten decay-resistant and ten susceptible trees from each of the progeny tests were analysed. In the heartwood of the resistant trees, the average total concentration of the stilbenes was 7.5 and 6.4xa0mg/g of dry weight, while in the heartwood of the susceptible trees the respective values were 5.0 and 4.7xa0mg/g. The difference between the decay resistant and susceptible trees was statistically significant in both progeny tests. The difference in concentration of total phenolics, analysed by the Folin-Ciocalteu method, was also significant. A high concentration of phenolics was connected to the low hygroscopicity of wood. The results support the argued hypothesis that the stilbenes make a contribution to the differences in the decay rate of natural wood substrate. On the other hand, the results show that the stilbenes alone do not explain the variation in decay rate.

Pollen competition and seed-siring success in Picea abies

Abstractu2002The aim of the present work was to study pollen-tube competition in Picea abies. Controlled crossings were performed with pollen mixtures including pairs of pollen lots with fast and slowly elongating pollen-tubes. Paternity analysis using isozyme markers was performed on the progenies in order to study whether the in vitro pollen-germination vigour corresponds to the proportion of seeds sired by the pollen donor. Paternal success was found to be unequal, 15 out of 23 crossings producing progeny that differed significantly from the hypothetical ratio of 1:1. The paternal contribution in the majority of the crossings was as expected: the pollen parent with more-vigorous in vitro germination sired more seeds than the less-vigorous pollen. In the case of two pollen mixtures, however, the seed-siring success summed over the maternal trees was the opposite to the expected value. Despite these aberrations, the results support the hypothesis that pollen-tube competition is one of the factors contributing to male fitness in P. abies. However, when all the other factors affecting pollination and seed set under natural conditions are taken into account, it is clear that the seed-siring success of a particular paternal genotype cannot be predicted reliably by measuring only the in vitro pollen vigour.

Genetic Parameters Regarding the Resistance of Pinus sylvestris Heartwood to Decay Caused by Coniophora puteana

Genetic variation in the durability of Pinus sylvestris L. heartwood to a brown rot fungus, Coniophora puteana, was studied using an in vitro decay test. Juvenile heartwood was sampled from 33-yr-old half-sib families growing in a progeny test and from their mothers in a clonal archive. The narrow-sense heritability for the heartwood weight loss was 0.37, and the coefficient of additive genetic variation was 28%. Heritability estimated by the regression of the offspring on mothers was 0.29, and the coefficient of genetic prediction was 0.24. These results indicated that it would be possible to improve the decay resistance of P. sylvestris heartwood by direct selection. According to the genetic correlation (r A = 0.36), selecting for heartwood density would result in an unfavourable response in weight loss caused by C. puteana. However, it appears that unknown environmental factors, which increase heartwood density, also decrease the heartwood weight loss (r E = -0.56). This result emphasizes the need for better understanding of the relationships among wood density, decay fungi, and environmental factors.

Wounding response in xylem of Scots pine seedlings shows wide genetic variation and connection with the constitutive defence of heartwood

In this greenhouse experiment, 3-year-old Scots pine (Pinus sylvestris L.) seedlings were wounded by drilling holes through the stem. In the xylem next to the wound, the concentration of resin acids (RAC) increased, and the production of extractives typical for heartwood (stilbenes) and knotwood (stilbenes and lignans) of mature trees was induced. The induced stilbenes were pinosylvin (PS) and pinosylvin monomethyl ether (PSM), and the lignans nortrachelogenin (NTG) and matairesinol (MR). There was positive phenotypic correlation between concentrations of the different extractives. Except for the RAC, the extractive concentrations showed no correlation with the size of the seedlings. The treated seedlings belonged to half-sib families, which enabled the estimation of the genetic parameters for the response variables. The proportion of heritable variation (heritability, h(2)) in the concentration of PS, NTG and MR varied between 0.71 and 1.03, whereas for PSM and RAC the heritability was lower (0.35 and 0.31). Genetic correlation was significant between PS and PSM (r = 0.55, P = 0.018), and between NTG and MR (r = 0.50, P = 0.033). Heritabilities were also estimated on the basis of the regression of the offspring on their mothers h(2)(0P). These estimates were assessed for the concentration of PS, PSM and RAC in the wound response area of the seedlings and correspondingly in the heartwood of their mothers. The heritability was highest for the concentration of PS h(2)(0P). The findings of this study support the suggestion that the wounding of Scots pine seedlings may facilitate the development of an early testing method for breeding heartwood durability.

Dielectric spectroscopy of Scots pine

Dielectric properties of Scots pine (42 trees) were compared with density, moisture content (MC), and resin acid content (RAC) (of heartwood). The samples were measured in frozen, green, conditioned and non-conditioned dry moisture states to evaluate the potential of dielectric spectroscopy in determining the wood characteristics at different stages of wood processing. Heartwood and sapwood parts of each sample were measured separately, and through-transmission measurement was conducted in longitudinal and tangential direction at frequencies from 1xa0MHz to 1xa0GHz. The MC and density correlated significantly with the dielectric parameters in both measurement directions but especially in longitudinal direction. The RAC of the heartwood correlated significantly with tanδ and ε″/(ε′xa0−xa01) of the green samples measured in the tangential direction at frequencies above 200xa0MHz. The correlation at 1xa0GHz was −0.56 for green samples, −0.66 for conditioned samples and −0.61 for non-conditioned samples (Pxa0<xa00.001, for all). The study suggests that the extractives also affect radio-frequency dielectric responses, which might be used for extractive analyses of pine heartwood.

Condensed conifer tannins as antifungal agents in liquid culture

Abstract In the last decades, many wood preservatives have been prohibited for their ecotoxicity. The present article is focusing on the conifer-derived condensed tannins as environment-friendly options for the substitution of artificial wood preservatives. Eight different tannin fractions were extracted from spruce cones, spruce barks, and pine cones. The parameters of tannin extraction, such as the methods of purification and concentration of active components in the extracts, have been investigated. The cone and bark extracts were tested for the growth inhibition of eight brown-rot fungi, three white-rot fungi, and four soft-rot fungi in liquid cultures. The cone tannins provided a more efficient fungal growth inhibition than bark tannins. Purification increased the antifungal properties of the extracts. The growth of brown-rot fungi was inhibited by the tannins already at low concentrations. However, the extracts were not effective against the white-rot or soft-rot fungi. More investigation is needed concerning the tannin source and the purification procedure of the extracts before tannins can be considered as an ecologically benign wood preservative.

The effect of brown-rot decay on water adsorption and chemical composition of Scots pine heartwood

Abstract• The effect of brown-rot (Coniophora puteana) decay on the water adsorption capacity and concentration of extractives of Scots pine (Pinus sylvestris L.) heartwood were studied by comparing corresponding properties of decayed and undecayed wood samples.• The samples derived from 39 felled trees having a large between-tree variation in the extractive concentrations, and subsequently in the mass loss in the decay test. The water adsorption capacity, expressed as equilibrium moisture content (EMC), was measured at a high relative humidity (RH ∼100%, 21 °C).• In contrast to the widely held belief, the water adsorption capacity of brow-rotted heartwood appeared to be significantly higher than that of undecayed heartwood.• The chemical composition of heartwood was changed radically by the fungus: the concentration of stilbenes, resin acids and free fatty acids decreased, while the concentration of soluble sugars increased as a result of decay. In addition, fungal sugars were found in the decayed samples. The concentration of total phenolics increased, which obviously reflected chemical changes in cell wall constituents other than extractives.• As a conclusion, the information concerning the hygroscopicity of brown-rotted wood might be valuable e.g. when carrying out repairs on buildings damaged by advanced decay.Résumé• Nous avons étudié l’effet de la présence de pourriture brune (Coniophora puteana) sur la capacité d’adsorption de l’eau et sur la concentration d’extractibles du bois de cœur du pin sylvestre (Pinus sylvestris L.) en comparant des échantillons contaminés et sains obtenus pour 39 arbres échantillonnés.• Dans les essais de décomposition, on obtient une grande variation entre arbres de la concentration en extractibles et de la perte de masse. La capacité d’adsorption de l’eau, exprimée comme l’humidité d’équilibre, a été mesurée à une humidité relative de 100 % à 21 °C.• Contrairement à ce qui était attendu, la décomposition augmente la capacité d’adsorption de l’eau du bois de cœur en atmosphère très humide. La différence entre arbres des variations de l’humidité d’équilibre (décomposé-contrôle) augmente significativement avec l’augmentation de la perte de masse.• La composition chimique du bois de cœur est radicalement modifiée par le champignon : la concentration de stilbènes, de résines acides et d’acides gras libres décroît tandis que la concentration de sucres solubles augmente, cela résultant de la décomposition. La concentration de composés phénoliques totaux, mesurée par le test de décomposition de Folin-Ciocalteu, augmente. De plus des sucres fongiques dérivant des hyphes de C. puteana ont été retrouvés dans les échantillons décomposés.• En conclusion, les informations concernant l’hygroscopicité du bois brun pourraient être utiles par exemple au moment de procéder à la réparation de bâtiments endommagés par une dégradation avancée.

Spectral and chemical analyses of mould development on Scots pine heartwood

AbstractScots pine heartwood specimens were exposed to mould in controlled humid atmosphere (RH 95%, Tu202f=20xa0°C)n and the responses of electrical impedance and Fourier transform infrared spectroscopy (EIS and FTIR)n methods were studied. The concentration of methanol soluble heartwood extractives and the emission ofn volatile organic compounds (VOC) were determined from the parallel samples. Results show that the spectraln responses and VOC emissions were related to the mould development. According to this study, VOC emissionsn might be used for discriminating mould susceptible and resistant samples. FTIR spectra showed thatn the relation of amide (1655xa0cm-1) and carbonyl peaks (1736xa0cm-1)n was significantly affected by mould. In the EIS analyses, there also were electrical parameters, whichn were significantly affected by mould. In conclusion, both spectral methods hold potential for non-destructiven mould detection and monitoring of mould development.n ZusammenfassungKiefernkernholzproben wurden im kontrollierten Feuchtklima (rLf 95%, Tu202f=u202f20xa0°C)n Schimmel ausgesetzt und mittels elektrischer Impedanzspektroskopie (EIS) und Fourieranalyse (FTIR) untersucht.n Die Konzentration an methanollöslichen Kernholzextraktstoffen und die Emission flüchtiger organischern Stoffe (VOC) wurden an Vergleichsproben bestimmt. Die Ergebnisse zeigten, dass die Banden der Spektralanalysenn und die VOC-Emissionen von der Schimmelentwicklung abhingen. Gemäß dieser Studie könnenn VOC-Emissionen für die Unterscheidung von schimmelanfälligen und resistenten Proben verwendetn werden. FTIR-Spektren zeigten, dass das Verhältnis zwischen den Amid- (1655xa0cm-1)n und Karbonyl-Peakhöhen (1735xa0cm-1) signifikant vom Schimmel beeinflusstn wurde. Die EIS-Analysen zeigten, dass elektrische Parameter ebenfalls signifikant vom Schimmel beeinflusstn wurden. Zusammenfassend kann gesagt werden, dass beide Verfahren eine Möglichkeit für dien zerstörungsfreie Schimmelerkennung und Überwachung der Schimmelentwicklung bieten.n

Detection of the effective refractive index of thermally modified Scots pine by immersion liquid method

The purpose of this study was to determine the effective refractive index of thermally modified Scots pine (Pinus sylvestris L.) wood specimens as a quantitative measure regarding the change of wood density which is due to the thermal modification. The refractive index of thermally modified Scots pine wood was obtained by introducing pine wood powder into an immersion liquid and measuring light backscattering with a homebuilt multifunction spectrophotometer. The present method provides useful information that in principle can be applied, for example, in the optimization of the thermal modification process and inspection of the quality of thermally modified wood.