15 © The Author(s). 2023 Open Access (CC) BY-NC license: htps://creatvecommons.org/licenses/by-nc/4.0/
Botanica Pacifca. 2023. 12(2):15–22 (This artcle belongs to the Special Issue dedicated to the memory of Alexey Shipunov)
DOI: 10.17581//bp.2023.12s02
ABSTRACT
Bark structure of Polylepis incana (Sanguisorbeae, Rosaceae) is described and com-
pared with that in related genera Cliffortia and Leucosidea. Tribe Sanguisorbeae shows
an extraordinary diversity of bark abscission patterns. The outermost bark por-
tions are peeling off along the non-conducting secondary phloem (Leucosidea,
Cliffortia ruscifolia), or along the periderm (C. strobilifera). The protective function is
performed by phellem (Leucosidea), or by sclerifed secondary phloem (Cliffortia).
In Polylepis, the separation layers occur in phellem and non-sclerifed phloem,
while a prominent protective layer is absent: its function is performed by multiple
uniseriate layers of suberized phellem cells. Such pattern of peeling bark has not
been reported yet elsewhere. Lenticels lack in Polylepis, but its phellem is similar
in its structure (probably, also in some functions) to stratifed flling lenticular
tissue. Smooth surface of Polylepis bark is maintained by permanent abscission of
thin layers representing an exterme case of the peeling type of bark architecture.
Keywords: Cliffortia, Leucosidea, Sanguisorbeae, secondary phloem, periderm, phellem, bark
abscission, dilatation
РЕЗЮМЕ
Осколский А.А., Мтемб А., Шипнов А.Б., Котина Е.Л. Анатоми
кор Polylepis (Rosaceae): рла стратииированна еллема вме-
сто еевиек? Polylepis incana (Sanguisorbeae,
Rosaceae).
Polylepis, Cliffortia Leucosidea
Sanguisorbeae. -
(Leucosidea, Cliffortia ruscifolia)
(C. strobilifera). Leucosidea
, Cliffortia – . Polylepis , -
,
: -,
-
.
. Polylepis ,
(, , ) -
.
Polylepis -
, -
(peeling) .
Клеве слова: Cliffortia, Leucosidea, Sanguisorbeae, , ,
, ,
Alexei A. Oskolski
1,2
*
e-mail: aoskolski@uj.ac.za
Alice Mthembu
1
e-mail: alicemthembu11@gmail.com
Alexey B. Shipunov
3
†
Ekaterina L. Kotina
2,4
e-mail: ELKotina@gmail.com
1
Department of Botany and
Biotechnology, University of
Johannesburg, South Africa
2
Komarov Botanical Institute,
St. Petersburg, Russia
3
Kyoto University, University Museum,
Kyoto, Japan
4
Saint Petersburg State Forestry
University, St. Petersburg, Russia
† deceased
* corresponding author
Manuscript received: 02.05.2023
Review completed: 10.06.2023
Accepted for publication: 18.06.2023
Published online: 20.06.2023
Alexei A. Oskolski
1,2,
*, Alice Mthembu
1
, Alexey B. Shipunov
3
&
Ekaterina L. Kotina
2,4
Bark anatomy of Polylepis (Rosaceae):
a loose stratified phellem instead of the
lenticels?
The genus Polylepis Ruiz & Pavón belonging to the
tribe Sanguosorbeae DC. (Rosaceae) comprises 45 species
of shrubs or trees native to the mid- and high-elevation
tropical Andes from northern Argentina to Colombia and
western Venezuela. Some species of this genus form forests
growing well above normal treeline at elevations over
4800 m. Thus, Polylepis appears to be the highest natural
occurring arborescent angiosperm genus in the Western
Hemisphere, and probably in the world (Simpson 1979,
Boza Espinoza & Kessler 2022).
The name of this genus, that is derived from Greek
words (many) and (scale), refers to distinctive
appearance of its bark. All species of Polylepis share brown
scaly bark which consists of numerous thin peeling layers.
The bark can be made up of more than 100 such layers
(Miyagawa 1975, Kessler 1995) and may be up to 3 cm thick.
The thickness and appearance of bark have certain syste-
matic value: the sections Sericeae and Reticulatae share thinner
bark that facks off in relatively thick scales comparing with
other sections of this genus (Boza Espinoza & Kessler
2022). Simpson (1979) suggested that thick loose bark of
Polylepis can serve as an insulation from severe diurnal varia-
tions of temperature and irradiation in tropical highlands;
this hypothesis has not been experimentally tested, however.
The anatomy of Polylepis bark has been studied by Miyagawa
(1975) and Lotova & Timonin (2005), but the structure and
formation of peeling periderm in this genus have not been
properly examined to date.
The multilayered peeling barks are characteristic not only
for Polylepis, but also for other woody genera of the tribe
Sanguisorbeae (Lotova & Timonin 2005). Kotina et al. (2017)
revealed some signifcant differences in bark structure bet-
ween Leucosidea Eckl. & Zeyh. and Cliffortia L., two genera
of this tribe from the southern Africa. Particularly, Leuco-
sidea has been found as distinctive from other Rosaceae in
having storied structure of the secondary phloem as well as