Monica Fongen

Lead Engineer

(+47) 974 81 706
monica.fongen@nibio.no

Place
Ås H8

Visiting address
Høgskoleveien 8, 1433 Ås

Abstract

Pathogen challenge of tree sapwood induces the formation of reaction zones with antimicrobial properties such as elevated pH and cation content. Many fungi lower substrate pH by secreting oxalic acid, its conjugate base oxalate being a reductant as well as a chelating agent for cations. To examine the role of oxalic acid in pathogenicity of white-rot fungi, we conducted spatial quantification of oxalate, transcript levels of related fungal genes, and element concentrations in heartwood of Norway spruce challenged naturally by Heterobasidion parviporum. In the pathogen-compromised reaction zone, upregulation of an oxaloacetase gene generating oxalic acid coincided with oxalate and cation accumulation and presence of calcium oxalate crystals. The colonized inner heartwood showed trace amounts of oxalate. Moreover, fungal exposure to the reaction zone under laboratory conditions induced oxaloacetase and oxalate accumulation, whereas heartwood induced a decarboxylase gene involved in degradation of oxalate. The excess level of cations in defense xylem inactivates pathogen-secreted oxalate through precipitation and, presumably, only after cation neutralization can oxalic acid participate in lignocellulose degradation. This necessitates enhanced production of oxalic acid by H. parviporum. This study is the first to determine the true influence of white-rot fungi on oxalate crystal formation in tree xylem.

Abstract

A method for quantitative determination of extractives from heartwood of Scots pine (Pinus sylvestris L.) using gas chromatography (GC) with flame ionization detection (FID) was developed. The limit of detection (LOD) was 0.03mg/g wood and the linear range (r=0.9994) was up to 10mg/g with accuracy within ±10% and precision of 18% relative standard deviation. The identification of the extractives was performed using gas chromatography combined with mass spectrometry (GC–MS). The yields of extraction by Soxhlet were tested for solid wood, small particles and fine powder. Small particles were chosen for further analysis. This treatment gave good yields of the most important extractives: pinosylvin, pinosylvin monomethyl ether, resin acids and free fatty acids. The method is used to demonstrate the variation of these extractives across stems and differences in north–south direction.

Abstract

In recent years chitosans have been investigated as a natural chemical for wood preservation against fungal decay, and chitosan in aqueous solutions has been used in impregnation studies. To evaluate the retention of chitosan after an impregnation process and to evaluate the fixation of chitosan in wood a method for determination of chitosan in wood and water samples has been developed based on acidic hydrolysis of chitosan to glucosamine followed by online derivatization by o-phthalaldehyde, chromatographic separation and fluorescent detection. For wood samples the method was linear up to 45mgg−1 chitosan in wood and had a recovery of 86%. The yield of chitosan in water was 87% at 1%(w/v) concentration.

Abstract

A method for determination of the climate gases CH4, CO2 and N2O in air samples and soil atmosphere was developed using GC-MS. The method uses straightforward gas chromatography (separation of the gases) with a mass spectrometric detector in single ion mode (specific determination).The gases were determined with high sensitivity and high sample throughput (18 samples h1). The LOD (3) for the gases were 0.10 L L1 for CH4, 20 L L1 for CO2 and 0.02 L L1 for N2O. The linear range (R2 = 0.999) was up to 500 L L1 for CH4, 4000 L L1 for CO2 and 80 L L1 for N2O. The samples were collected in 10 mL vials and a 5 L aliquot was injected on column.The method was tested against certified gas references, the analytical data gave an accuracy within 5% and a precision of 3%. The presence of 10% by volume of C2H2 (often used experimentally to prevent N2 formation from N2O) did not interfere with detection for the targeted trace gases.

Abstract

A home designed diffusion chamber was used during the isolation of fluoride from plant material. The chamber contained two beakers, one for the sample (milled plant material) and the other for the trapping solution (0.1M NaOH). Hexamethyldisiloxane (HMDS) in 3.5M perchloric acid was added into the sample beaker through a septum, after the chamber was closed.Fluoride in the sample reacts with HMDS and forms the volatile trimethylfluorosilane (TMFS), which is trapped and hydrolyzed to fluoride. The diffusion time was 2h and 20 samples were handled at the same time. The fluoride concentration was determined by a flow injection analysis (FIA) system using an ion selective electrode (about 50 samples/hour).The results by acid extraction were compared to the results obtained after an ashing/alkaline fusion. Both a certified sample of timothy grass (NIST 2695, high level) and more typical vegetation from forest were analyzed. For the timothy grass, the recovery increased from 48 to 84% when ashing/alkali fusion was used before the diffusion. However, higher recovery was not obtained by using ashing/alkaline fusion for the determination of fluoride in natural vegetation from forest. Acid extraction in combination with addition of HMDS was sufficient as pretreatment in these types of plant materials.The method was routinely used for the determination of fluoride both in research and forest monitoring.

Abstract

This article describes in brief the chemical analytical program at The Norwegian Forest Research Institute in 2000. Due to a continuous effort to develop and to improve analytical methods to meet the demands of forest research in Norway, the four earlier summaries of our methods (Ogner et al. 1975, 1977, 1984, 1991) are now outdated. This article replaces the previous ones and describes only those procedures currently being used for the analysis of water, plant and soil samples