The anatomy of »blue ring« in the wood of Pinus nigra: Anatomija »modre branike« v lesu črnega bora Pinus nigra | The anatomy of »blue ring« in the wood of Pinus nigra: Anatomija »modre branike« v lesu črnega bora Pinus nigra

English. Tree-ring features are widely used to identify specific climate, environment and stress events affecting plant life. Cold temperatures can mainly affect the last phase of cell differentiation by interfering in the process of cell wall lignin deposition. Recently, it was found out that the effect of cold temperature on lignification is visible in wood microsections double stained with astra blue which stains cellulose, and red safranin which stains lignin. This new tree-ring feature was called »blue ring«. In this study, we investigated the anatomical morphology of blue rings in transverse and longitudinal wood microsections of three European black pine trees (Pinus nigra Arnold) growing above the treeline. We aim to understand if the lack of lignification is consistent along the entire tracheid length and whether or not pits, responsible for water transport from one tracheid to another, are lignified. The results show that the lack of lignification extends along the entire tracheids cell wall, including bordered pits. Based on our observations we speculate that blue ring occurrence decreases the safety of water transport and wood mechanical properties.

Slovenian. Lesno-anatomske posebnosti branik pogosto uporabljamo za ugotavljanje specifičnih dogodkov v zvezi s podnebjem, okoljem in stresom, ki jim je izpostavljeno drevo med rastjo. Med pomembnimi dejavniki so nizke temperature, ki lahko vplivajo na diferenciacijo lesa, predvsem na odlaganje lignina. Nedavno so ugotovili, da je učinek nizkih temperatur na potek lignifikacije viden na mikroskopskih preparatih lesa, ki jih dvojno obarvamo s safraninom (ki obarva lignin rdeče) in astra modrim (ki obarva celulozo modro). To novo anatomsko posebnost so poimenovali »modra branika«. V študiji smo raziskali anatomsko zgradbo modrih branik na prečnih in vzdolžnih (radialnih) prerezih lesa črnih borov (Pinus nigra Arnold), ki so rasli nad zgornjo gozdno mejo. Cilj raziskave je bil pojasniti, ali je pomanjkljiva lignifikacija vidna po celotni dolžini traheid in ali so obokane piknje, ključne za prevajanje vode, lignificirane. Rezultati kažejo pomanjkljivo lignifikacijo vzdolž traheid in v obokanih piknjah. Na osnovi rezultatov sklepamo, da pojav modre branike zmanjšuje varnost transporta vode in vpliva na slabše mehanske lastnosti lesa.