Biochemical Aspects of the Spiral Grain Formation in Scots Pine (Pinus Sylvestris L.) Wood. Some Differences and Similarities with Biochemical Indicators of Abnormal Xylogenesis in Karelian Birch (Betula Pendula Roth Var. Carelica (Mercl.) Hämet-Ahti)

Background: AOS enzymes can be biochemical indicators of abnormal xylogenesis in Scots pine, and this mechanism has similar features with the metabolic base of abnormal xylogenesis in Karelian birch.

Objective: AOS enzymes' activity in 150-300-year-old Pinus sylvestris L. wood with straight-- grained wood and right-twisted spiral-grained wood, expressed in varying degrees (5-20 angle), grew in three sample plots in lingonberry and blueberry pine forest stands of different ages (100-300 years) in the middle taiga subzone in the Republic of Karelia.

Methods: Plant tissues were ground in liquid nitrogen in a uniform mass and homogenized at 4°C in the buffer containing 50 mM HEPES (pH 7.5), 1 mM EDTA, 1 mM EGTA, 3 mM DTT, 5 mM MgCl2 and 0.5 mM PMSF. After 20 min extraction, the homogenate was centrifuged at 10000 g for 20 min (MPW-351R, Poland). The sediment was washed in the buffer thrice. The pooled supernatant and sediment were dialyzed at 4°C for 18-20 h against a tenfold diluted homogenization buffer. The enzymes' activity was determined spectrophotometrically (Spectrophotometer SF-2000, OKB Spectr, Russia). Proteins in the extracts were quantified by the method of Bradford.

Results: The study showed that the activity of SS, ApInv, CAT, POD and PPO in xylem and PPO in phloem were biochemical indicators for abnormal wood of P. sylvestris. We noticed an increase in sucrose metabolism in the apoplast and the activity of POD and PPO under spiral-grain wood formation like under figured wood formation earlier. We assume that the alternative pathway of sucrose metabolism (an indicator of abnormal xylogenesis in B. pendula var. carelica plants) that lead to restructuring of AOS enzymes have the same biochemical regularities in the spiral-grain wood formation in P. sylvestris.

Conclusion: The study showed that the differences in the AOS enzyme's activity in P. sylvestris during the formation of straight-grained and spiral-grained wood were revealed for the first time. The increased CAT, POD and PPO activities in xylem with a decrease in SS and an increase in Ap- Inv during spiral-grained wood formation can be biochemical markers of these structural anomalies. Metabolic regularities found in the AOS enzyme complex during spiral-grained wood formation do not contradict those found earlier during figured wood formation in B. pendula var. carelica. The identified patterns can form the base for diagnostics of P. sylvestris wood quality in forest seed plantations and in their natural growth, which is necessary both for fundamental science and in various industry areas while high-quality material harvesting.