Pekka Saranpää

Crystallinity of wood and the size of cellulose crystallites in Norway spruce (Picea abies)

X-ray diffraction was used to study variations in the crystallinity of wood and the average thickness and length of the crystallites of cellulose as a function of the number of the year ring in Norway spruce [Picea abies (L.) Karst.]. The crystallinity increased from ring 4 to ring 10 from the pith and was constant after ring 10. The crystallinity of mature wood was about 30% ± 5%. The average thickness and average length of the crystallites were 3.2 ± 0.1 nm and 28 ± 2 nm, respectively; and no systematic variation of these values with the number of the year ring was observed. The mean microfibril angle decreased near the pith but was constant in the mature wood.

Expression profiling of the lignin biosynthetic pathway in Norway spruce using EST sequencing and real-time RT-PCR.

Lignin biosynthesis is a major carbon sink in gymnosperms and woody angiosperms. Many of the enzymes involved are encoded for by several genes, some of which are also related to the biosynthesis of other phenylpropanoids. In this study, we aimed at the identification of those gene family members that are responsible for developmental lignification in Norway spruce (Picea abies (L.) Karst.). Gene expression across the whole lignin biosynthetic pathway was profiled using EST sequencing and quantitative real-time RT-PCR. Stress-induced lignification during bending stress and Heterobasidion annosum infection was also studied. Altogether 7,189 ESTs were sequenced from a lignin forming tissue culture and developing xylem of spruce, and clustered into 3,831 unigenes. Several paralogous genes were found for both monolignol biosynthetic and polymerisation-related enzymes. Real-time RT-PCR results highlighted the set of monolignol biosynthetic genes that are likely to be responsible for developmental lignification in Norway spruce. Potential genes for monolignol polymerisation were also identified. In compression wood, mostly the same monolignol biosynthetic gene set was expressed, but peroxidase expression differed from the vertically grown control. Pathogen infection in phloem resulted in a general up-regulation of the monolignol biosynthetic pathway, and in an induction of a few new gene family members. Based on the up-regulation under both pathogen attack and in compression wood, PaPAL2, PaPX2 and PaPX3 appeared to have a general stress-induced function.

Effect of Growth Rate on Fibre Characteristics in Norway Spruce (Picea abies (L.) Karst.)

Summary To study the effect of growth rate on fibre characteristics and their variations in Norway spruce, trees were sampled in a nutrient optimisation experiment in northern Sweden. Data was collected from 24 trees (40 years old) from fertilised and control plots after 12 years of annual nutrient application, as well as from older trees outside the experimental area. Fibre length, fibre diameter, cell wall thickness, lumen diameter and cell wall percentage were measured from every third annual ring at breast height and at a height of 4 m. Fibre properties, as well as their standard deviation, were closely related to ring number and distance from the pith. Intra-ring variation of fibre characteristics was high compared to their variation between trees. Fertilisation reduced fibre length and cell wall thickness, but increased fibre and lumen diameter in rings of the same age. The difference in fibre width, cell wall thickness and lumen diameter between fertilised and control trees was less apparent, but a greater difference in fibre length was found between the treatments with regard to distance from the pith. There was a similar effect of fertilisation on fibre properties in early- and latewood. The effect of enhanced growth rate was less pronounced at a height of 4 m (near the pith) than at breast height (in older rings). It was demonstrated that it is possible to model intra-tree variability of fibre characteristics using ring width and cambial age as independent variables. Models presented are, however, limited by the relatively young age of the sample trees used.

Variation of non-structural carbohydrates in silver birch (Betula pendula Roth) wood

Abstract. Non-structural carbohydrates in silver birch (Betula pendula Roth) wood were analysed in a 7-year-old clone and in five mature stems. The analysis was conducted to obtain more detailed information on seasonal fluctuation of these components and of the tree-to-tree variation and within stem variation. The sugars were analysed by GLC-MS. The smallest total soluble sugar amounts (consisting of sucrose, fructose, glucose, raffinose and myo-inositol) in young trees were measured during mid-summer (ca. 0.3%) and the largest while in dormancy (ca. 1.6% on wood dry weight basis). Raffinose was detected in autumn as a minor component. The proportion of monosaccharides and the amount of myo-inositol were largest during growth. Compared to other studies silver birch showed more evident seasonal fluctuation in soluble sugars than evergreen tree species. The sugar amount in mature stems was approximately at the same level as in young trees that had the same felling time. Tree-to-tree variation in the non-structural carbohydrates in the mature wood was fairly large. However, the amount of total soluble sugars, sucrose and glucose showed significant variation within the stem. The amount of these sugars was largest in samples that were taken close to the cambium. Starch was also detected close to pith. According to the heartwood definition and starch measurement results in this paper, it could be stated that silver birch does not form heartwood.

Microfibril angle of Norway spruce [Picea abies (L.) Karst.] compression wood: comparison of measuring techniques.

The structure of cellulose, especially the microfibril angles (MFAs), in compression wood of Norway spruce [Picea abies (L.) Karst.] was studied by wide- and small-angle X-ray scattering and polarizing microscopy. On the basis of the X-ray scattering experiments the average MF As of the cell wall layers S2 and S1 of the studied sample are 39‡ and 89‡, respectively; and the average diameter and length of the cellulose crystallites are 2.9 and 20.0nm, respectively. The average of the whole MFA distribution is shown to agree with the one obtained by polarizing microscopy of macerated fibers.

Effect of growth rate on mean microfibril angle and cross-sectional shape of tracheids of Norway spruce

The variation of the mean microfibril angle (MFA) and the shape of the cross-section of lumen with the distance from the pith in fast grown Norway spruce were studied by X-ray scattering and optical microscopy. The samples were from stems of a clone of Norway spruce [ Picea abies (L.) Karst.] grown in a fertile site at Nurmijärvi, southern Finland Both the mean MFA and the circularity index of the lumen of the fast-grown trees decreased more gradually as the distance from the pith increased than those in reference trees grown in a medium fertility site. However, in mature wood the mean MFA reached the same level in fast-grown trees as in reference trees (5°–10°) but the cross-sections of the cells remained more circular in fast-grown trees than in reference trees. The dependence of the mean MFA on the distance from the pith was similar for earlywood and latewood, but the values of the mean MFA of latewood were systematically smaller than those of earlywood. Two different X-ray diffraction geometries were compared from the points of view of biology and data analysis.

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.

Basic density, longitudinal shrinkage and tracheid length of juvenile wood of Picea abies (L.) Karst

Variation in the growth ring width, basic density, longitudinal shrinkage and tracheid length was investigated in the juvenile wood of Norway spruce samples taken from different heights in the stem. Annual height increments were cut from the ten youngest shoots from trees of three different heights. By this method the properties of an individual growth ring could be analysed without taking samples from each ring. Sixteen tree tops of an average stem height of 8, 15 and 25 m were analysed. Basic density was low in the first shoot, highest in the second or third one and decreased gradually thereafter. Longitudinal shrinkage was highest close to the pith and decreased to about 0.2% in the outer rings. Tracheids were only ca. 1 mm long close to the pith and their length increased sharply towards the tenth shoot. The properties of juvenile wood varied with the height in the stem. Longitudinal shrinkage around the pith seemed to increase with increasing height and basic density was highest at 25 m stem height. ...

Soluble carbohydrates of Pinus sylvestris L. sapwood and heartwood

SummaryThe amounts of glucose, fructose, sucrose, arabinose/galactose, raffinose/stachyose and starch were investigated in the outer sapwood, innermost sapwood, transition zone and heartwood of four stems of Pinus sylvestris L. The samples were taken in October and the determination of the compounds was done enzymatically. It was not possible to distinguish arabinose from galactose and raffinose from stachyose. The amounts of glucose, fructose and sucrose were greatest in the outer sapwood and decreased gradually towards the innermost sapwood and the heartwood. In the outermost heartwood glucose, fructose and sucrose were only present in trace amounts. Raffinose/stachyose showed highest concentrations in the outer sapwood and decreased towards the heartwood. In contrast, the concentrations of arabinose/galactose increased towards the heartwood and the greatest amount was found in the inner heartwood. When identified by thin-layer chromatography (TLC), arabinose was found to be present in greater amounts than galactose. The amount of starch decreased markedly towards heartwood. However, the amounts of sugars in all the studied stems was very variable. The changes in the amounts of carbohydrates in the different zones of the stems and the possible relationships of these phenomena with heartwood formation are discussed.

Effects of long-term nutrient optimisation on stem wood chemistry in Picea abies

Abstract. The aim of the present study was to determine how long-term nutrient optimisation of Norway spruce stands affects the chemical composition of stem wood. Material for the study was collected from Flakaliden (Sweden) where Norway spruce [Picea abies (L.) Karst.] stands have been grown either without fertilisation or under nutrient optimisation treatment, by supplying a complete nutrient mix in the irrigation water every 2nd day during the growing season. The experiment was established in 1987 and in the autumn of 1998, 12 trees were harvested both in control (no fertilisation) and irrigated-fertilised (IL) stands. The increased growth rate caused by the IL treatment affected the chemical composition of the stem wood. The most pronounced effect was a 7% increase in lignin concentration caused by the IL treatment. Increases in concentrations of acid-soluble lignin (1.1-fold), extractives (1.2-fold), soluble sugars (1.3-fold), sterols (1.3-fold) and dehydroabietic acid (1.6-fold) as well as a decrease in the proportional quantity of terpinolene were also found. These results demonstrate that nutrient optimisation affected the chemical composition of Norway spruce wood, which may influence the suitability of such wood for specific end-use purposes.