ISSN 10214437, Russian Journal of Plant Physiology, 2015, Vol. 62, No. 3, pp. 381–389. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © N.A. Galibina, L.L. Novitskaya, M.S. Krasavina, Yu.L. Moshchenskaya, 2015, published in Fiziologiya Rastenii, 2015, Vol. 62, No. 3, pp. 410–419.
Karelian birch (
form of silver birch is a unique object convenient for
elucidating the mechanisms of morphogenesis in trees.
Compared to other woody species, Karelian birch dis
plays particularly distinct and diverse structural anoma
lies of trunk tissues that appear in plant development
and exhibit high endogenous variability .
Specific texture of Karelian birch wood emerges as
a result of deviations in cambial activity [1, 2]. In
zones of structural anomalies, the program of cell
death responsible for the formation of xylem fibrous
tracheids and vessels and phloem sieve tubes is not
commenced; the differentiating cambial derivatives
retain the protoplast and turn into storage parenchyma
cells that accumulate abundant lipids and tannins .
Disorders in differentiation of xylem and phloem con
ducting elements are visually evident in appearance of
large aggregations of parenchymal cells producing a
characteristic pattern on wood sections (Fig. 1).
Multiyear investigations have detected a series of
physiological and biochemical features associated
with the formation of patterned wood; it was suggested
that the disturbance of cambial activity and develop
ment of structurally abnormal conducting tissues
results from elevated content of sucrose in the con
ducting phloem and the cambial zone . Unlike
other sugars, sucrose has a profound morphogenetic
effect: fluctuations of its level in the cambial zone
switch over the cell differentiation from xylem con
ducting elements to phloem elements. The increase in
sucrose content above a certain level is known to
inhibit cambial activity and differentiation of con
ducting elements [3, 4]. Sucrose and the monosaccha
rides produced upon its cleavage affect the functional
state of sugarsensitive proteins in cell membranes,
which modifies the pattern of gene expression [5, 6].
Utilization of sucrose in sink tissues involves the
enzymes of sucrose hydrolysis: invertase and sucrose
synthase (e.g., [5, 7, 8]). Sucrose synthase (SS) is
ubiquitous in plants, but its greatest activity was
detected in sink tissues . The intracellular SS occurs
in a free state or is bound to plasma membrane [8, 10].
Activity of Sucrose Synthase in Trunk Tissues of Karelian Birch
during Cambial Growth
N. A. Galibina
, L. L. Novitskaya
, M. S. Krasavina
, and Yu. L. Moshchenskaya
Institute of Forestry, Karelain Research Center, Russian Academy of Sciences,
ul. Pushkinskaya 11, Petrozavodsk, 185910 Russia;
Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276 Russia
Received August 22, 2014
—Activity of sucrose synthase (SS) and the content of starch were studied in the xylem and phloem
of two forms of 40yearold trees of
Roth: common silver birch (
Karelian birch (
). In order to reveal the initial signs of wood patterning, we used
8yearold trees of Karelian birch that did not yet exhibit visible deviations from normal growth (trees with
unpatterned wood) and those where formation of structural trunk anomalies already commenced (trees with
patterned wood). Investigation was conducted during the period of cambial growth: in June growth was active
and in July growth was suppressed by weather conditions. In June we found a high SS activity in the xylem of
40yearold plants of common birch. Retardation of growth of common birch in July was accompanied by
the decrease in SS activity in the xylem and by accumulation of starch, especially in the phloem. In 8year
old trees of Karelian birch with unpatterned wood, the SS activity in the xylem was lower than in common
birch trees, while the content of starch in the phloem was higher. In the xylem of trees with patterned wood,
the highest activity of SS was approximately 2.5 times lower than in the trees with unpatterned wood. The
lower SS activity in the xylem of patterned trunk trees was not associated with starch accumulation in the
phloem. We propose that low SS activity during cambial growth reduces sink capacity of xylem tissues, thus
leading to a considerable increase in the sucrose content in the phloem, which can alter the program of cell
development in the cambial zone of Karelian birch.
Keywords: Betula pendula
, cambial growth, sucrose synthase, starch
: SS—sucrose synthase.