Anatomske, histokemične in mikrookoljske spremembe v mehansko poškodovanem lesu bukve (Fagus sylvatica) in doba (Quercus robur) : doktorska disertacija

Merela, Maks (author), Oven, Primož (mentor), Serša, Igor (comentor), Torelli, Niko (reviewer), Batič, Franc (reviewer)

Pri navadni bukvi (Fagus sylvatica L.) in hrastu dobu (Quercus robur L.) smo raziskali anatomske, histokemične in mikrookoljske spremembe po mehanskem poškodovanju. Spremembe vlažnosti po poškodbi smo spremljali s 3D MR slikanjem na živih drevesih in vivo in na segmentih poškodovanih vejic, na katerih smo opravili tudi klasično svetlobno mikroskopijo ter mikro PIXE in FTIR analize. 3D MR slikanje je razkrilo zgradbo in proces sušenja in ponovnega navlaževanja poškodovanih tkiv. Pri obeh vrstah se je v treh dneh po poškodbi pojavila površinska izsušitev tkiv, ki se je nato v stožčasti obliki razširila globlje v vejico. Pri bukvi se je med tretjim in osmim dnem po poškodbi povečala vlažnost na mestu predhodne izsušitve. Sledila je ponovne navlažitev tega tkiva, pri čemer se je izoblikovala vlažna reakcijska cona med izsušenim in nepoškodovanim intaktnim tkivom. Povečano vlažnost so prav tako izkazovala novo nastala poranitvena tkiva, nastala na robu poškodbe. V reakcijskih conah bukve so bili lumni traheje zapolnjeni s skleroznimi in suberiziranimi tilami ter depoziti, ki so bili prisotni tudi v lumnih celic in v večini pikenjskih odprtin. Suberizirane celice so sestavljale neprekinjeno plast, ki je pri bukvi segala od periderma preko skorje vzdolž barierne cone in se kot sestavni del reakcijske cone nadaljevala v les nastal pred ranitvijo. V reakcijskih conah doba so bili prav tako prisotni depoziti in tile, za razliko od bukve pa izostane jasno definirana vlažna reakcijska cona in suberizacija til, umanjkajo pa tudi novonastala poranitvena tkiva. Odziv na mehansko poškodbo pri dobu predstavljajo predvsem okluzije v trahejah, parenhimu in vlaknih. Prvi element nastanka reakcijske cone pri bukvi predstavlja ponovno navlaževanje predhodno izsušenih tkiv. Veliko vlažnost in vlažnostni gradient vzdržuje povečana koncentracija kalija. Drugi pomemben element nastanka reakcijske cone predstavljajo anatomske in histokemične spremembe v tkivih reakcijske cone. Suberin, prisoten na tilah in v barierni coni, s svojimi lastnostmi dodatno prispeva k zaščitni funkciji strukturno modificranih tkiv reakcijske cone. Reakcijska cona pri bukvi tako predstavlja vlažnostno bariero, ki preprečuje izsuševanje nepoškodovanega intaktnega dela, s svojimi antifungicidnimi in antimikrobnimi lastnostmi pa dodatno ščiti tkiva pred okužbami.

• Language: Slovenian
• Keywords: mehanske poškodbe, bukev, Fagus sylvatica L., hrast dob, Quercus robur L., reakcijska cona, 3D MRI, anatomija, mikro PIXE, FTIR, vlažnost
• Work type: Dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: BF - Biotechnical Faculty
• Place of publishing: Ljubljana
• Publisher: M. Merela
• Year: 2008
• Number of pages: XVIII, 221 str., [13] str. pril.
• PID: 20.500.12556/RUL-148037
• UDC: 630*852
• COBISS.SI-ID: 1692041
• Publication date in RUL: 26.07.2023

Secondary language

• Language: English
• Title: Anatomical, histochemical and microenvironmental changes in mechanical injured wood of Beech (Fagus sylvatica) and pedunculate oak (Quercus robur) : doctoral dissertation

Abstract

Anatomical, histochemical and microenvironmental changes after mechanical injury were investigated at common beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.). Water content changes after wounding were monitored by 3D MR imaging of living trees in vivo and by imaging of segments of injured branches. On the same segments traditional light microscopy, micro PIXE and FTIR analysis were made. 3D MR imaging revealed structures and dehydration as well as rewetting process in wounded tissues. At both species, tissues dehydrated at the surface of the wound in three days after wounding. Dehydration spread in cone shape pattern deeper in the branch thereafter. At common beech moisture content increased in previously dehydrated region between three and eight days. This tissue dehydrated again, whereas moist reaction zone formed between dehydration and intact tissue. Water content increased also in new tissues formed on the edge of the wound. In reaction zone of common beech vessels were blocked by sclerotic and suberized tyloses, cell lumina as well as most of pit apertures were filed with deposits. Suberized cells formed continuous layer in common beech extending from periderm trough the inner bark along barrier zone and continued in the xylem formed before wounding as constitutive part of reaction zone. Deposits and tyloses were also present in the reaction zone of oak however moist reaction zone, suberized tyloses and new wound-tissues were missing. Occlusion of vessels, parenchyma and fibers appear to be the main response to mechanical injury in investigated pedunculate oaks. The first element of reaction zone formation in common beech is re-moistening of previous dehydrated tissue. High moisture content and moisture gradient is supported by high concentration of potassium. Second important element of reaction zone formation is anatomical and histochemical changes in the tissues of reaction zone. Nature of suberine present in tyloses and in cells of the barrier zone additionally contributes to the protective function of structural modified tissues of reaction zone. Reaction zone at common beech presents moisture barrier preventing the dehydration of healthy intact tissue as well as by its antifungicide, antimicrobial and antibacterial nature protects the tissue against infections.

• Keywords: mechanical injury, beech, Fagus sylvatica L., pedunculate oak, Quercus robur, reaction zone, 3D MRI, anatomy, micro PIXE, FTIR, moisture