An Indicating Role of Antioxidant System Enzymes at the Stage of Active
Structural Anomalies Formation in Karelian Birch (Betula pendula Roth
var. carelica (Mercl.) Hämet-Ahti)
Authors: Nikerova Kseniya Mihajlovna , Galibina Natalia Alekseevna , Sofronova Irina Nikolaevna , Borodina Marina Nikolaevna , Moshchenskaya Yuliya Leonidovna , Tarelkina Tatiana Vladimirovna , Klimova Anna Vladimirovna , Novitskaya Ludmila Lyudvigovna 
Published: March 2023

Introduction:

A complex study of the antioxidant system enzymes (AOS) is an important subject
of biochemical research; changes in the activity of these enzymes can be used as a biochemical marker of
various processes in plants. At the same time, practically little attention has been paid to describing the
regularities of these enzymatic reactions in different wood formation processes, such as xylogenesis. This
article discusses the outcomes of different behaviors of AOS enzymes, which are involved in both the
redistribution of the ROS balance and phenolic compounds at the early stages of wood formation in young
plants of silver birch (Betula pendula Roth) with straight-grained wood and Karelian birch (Betula pendula
Roth var. carelica (Merckl.) Hamet-Ahti) with non-figured and figured parts within the single trunk.

Background:

Spectrophotometric determination of AOS enzymes’ activity can be used as a biochemical
marker in the different wood formation processes, including xylogenesis. In this study, we studied structural
anomalies of the woody plant trunk of Karelian birch (Betula pendula Roth var. carelica (Merckl.) Hamet-
Ahti).

Objective:

This study aimed to study AOS enzymes’ activity in 12-year-old plants of silver birch (Betula
pendula Roth) with straight-grained wood and Karelian birch (Betula pendula Roth var. carelica (Merckl.)
Hamet-Ahti) with non-figured and figured parts within the single trunk.

Methods:

Plant tissues were ground in liquid nitrogen to 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:

We observed different behaviors of the studied enzymes involved in both the redistribution of the
ROS balance and phenolic compounds with subsequent lignification even at the early stages of wood
formation in young plants and even in different trunk parts within a tree, which was consistent with results
obtained earlier on adult plants. High SOD activity in the phloem compared to the activity in the xylem was
accompanied by higher CAT activity. The POD/SOD ratio was significantly higher in the figured trunk parts
in Karelian birch compared to other variants in the xylem and higher in Karelian birch plants compared to
plants of common birch in the phloem. The CAT/POD ratio was significantly higher in plants with no signs
of anomalies. The high POD and PPO activity in the xylem of figured trunk parts and in the phloem of
figured and non-figured trunk parts of B. pendula var. carelica can be associated with the high activity of
apoplast invertase.

Conclusion:

The study showed that at the stage of active formation of structural anomalies in the figured
trunk parts in young plants of Karelian birch, hydrogen peroxide utilization occurred mainly due to increased
POD activity. An increase in PPO activity in the trunk of figured plants could also be considered an indicator
of the formation of structural anomalies. At the same time, in areas with developing abnormal wood, the
POD/SOD ratio increased, and the CAT/POD ratio decreased, indicating a fine-tuning of the balance
between superoxide radical and hydrogen peroxide, which, when changed, might regulate the rearrangement
of xylogenesis towards proliferation in relation to differentiation.