Vpliv staranja na strukturne lastnosti lesa hrasta

Belec, Alen (author), Čufar, Katarina (mentor), Straže, Aleš (comentor)

Raziskali smo strukturne in kemijske spremembe v jedrovini lesa hrasta (Quercus sp.) povezane s staranjem. Vzorčili smo konstrukcijski les različne starosti iz več objektov v Sloveniji. Starost lesa smo določili dendrokronološko, strukturne in anatomske lastnosti pa s svetlobno mikroskopijo (svetlo polje, polarizirana svetloba, epi-fluorescenca) ter z infrardečo spektroskopijo s Fourierjevo transformacijo (FT-IR spektroskopijo). Potrjena splošna vizualno temnejša barva starejše hrastove jedrovine je bila med drugim odvisna od variabilne anatomske lesne zgradbe, z značilnim vplivom deležev kompleksov traheid, trahej, libriformskih vlaken in trakov. S FT-IR določena deleža hemiceluloz in lignina sta se primerjalno z osnovnimi lesnimi komponentami v procesu staranja hrastovine zmanjšala. Zmanjšanje deleža hemiceluloz je bilo statistično značilno, zmanjšanje deleža lignina pa neznačilno. Z uporabo polarizirane svetlobe smo v procesu staranja hrastovine zaznali tudi degradiranje celuloze. Pri vzorcu subfosilnega lesa, starem več kot 600 let, ki se je ohranil v z vodo napojenem stanju, pa smo z uporabo vseh tehnik zaznali povečan delež lignina ter zmanjšan delež celuloze in hemiceluloz. Raziskava je pokazala, da so spremembe v nekaterih podobno starih vzorcih v procesu staranja različni, kar pripisujemo variabilnim (in delno nepoznanim) pogojem izpostavitve lesa tekom uporabe.

• Language: Slovenian
• Keywords: hrast, Quercus sp., les, staranje, svetlobna mikroskopija, infrardeča spektroskopija
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: BF - Biotechnical Faculty
• Publisher: [A. Belec]
• Year: 2017
• PID: 20.500.12556/RUL-95678
• UDC: 630*561.24
• COBISS.SI-ID: 2811273
• Publication date in RUL: 21.09.2017

BELEC, Alen, 2017, Vpliv staranja na strukturne lastnosti lesa hrasta [online]. Bachelor’s thesis. A. Belec. [Accessed 17 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=95678

Secondary language

• Language: English
• Title: EFFECT OF AGEING ON STRUCTURAL PROPERTIES OF OAK WOOD

Abstract

We examined structural and chemical changes in heartwood of oak (Quercus sp.), related to wood ageing. The research was made on samples of construction wood of various ages from different objects in Slovenia. The age of wood was determined dendrochronologically. Structural and anatomical properties were determined with help of light microscopy (techniques: bright field, polarized light, epi-flourescence) and Fourier Transform Infra Red (FT-IR) spectroscopy. It has been visually confirmed that the heartwood becomes visually darker due to ageing. Its colour proved to depend on variable wood anatomy, with different proportions of vessels, traheids, libriform fibres and rays. FT-IR spectroscopy showed that the percentage of hemicellulose and lignin decreased in comparison with basic wood components during the process of ageing. The decrease of hemicellulose proportion was statistically significant, whereas the decrease of lignin was not. Degradation of cellulose during the ageing was also shown by using polarized light. In the case of more than 600 years old sample of subfossil wood, which was preserved underwater, all techniques confirmed an increased proportion of lignin and decreased proportion of cellulose and hemicellulose. Different degree of changes in similarly old samples could be ascribed to variable (and partly unknown) conditions of wood exposure during its service life.

• Keywords: oak, Quercus sp., wood, ageing, light microscopy, infrared spectroscopy