|
40
,
M.
Akhalkatsi
&
J.
Wagner:
al pecularities, the life histories, and the dynamics of seed formation are pre¬
sented.
Material and methods
Plant material.
Gentiana pyrenaica
(syn.
Gentiana djimilensis
C.
Koch)
is a perennial
mountain plant distributed in the Pyrenees, the Carpathians, in SW Bulgaria, Anatolia and
Iran, and in the Caucasus
(Gagnidze
1985,
Tutin
&
al.
1972).
In the Central Caucasus this
species can be found between
2000
and
3500
m s.m. Depending on the altitude the flow¬
ering period is June to July, with a possible second flowering in August to October. The
plant material for the present investigation was collected in July at
3100
m s.m. in the sub-
nival zone on Mt. Sabertse in the Central Caucasus (Kazbegi region, Georgia).
Gentianella caucasea
(syn.
Gentiana caucasica
Bieb.)
is an annual plant, distributed in
Anatolia, Iran and in the Caucasus
(Gagnidze
1985).
Various morphological types with
different flowering times from summer to late autumn occur in widely differing habitats
from the
subalpine
to the subnival zone
(Akhalkatsi
&
Wagner
1996).
Plant material was
collected in July at
1950
m s.m. in the
subalpine
zone on the lower slopes of Mt. Kuro in
the Central Caucasus (Kazbegi region, Georgia).
Gentianella germanica
(syn.
Gentiana germanica
Willd.)
is an annual or biennial spe¬
cies, occurring from the colline up to the alpine zone in West and Central Europe and in
the mountain regions of the Balkans
(Meusel
&
al.
1978).
Like
G. caucasea,
this species
occurs in ecotypic variants, showing differences in their morphological characteristics and
time of flowering
(Wettstein
1895,
Zopfi
1991).
The plant material was sampled in Octo¬
ber from a biennial population at
2000
m s.m. in the
subalpine,
zone of the Mt. Patscher-
kofel in the Central Alps (Tyrol, Austria). Herbarium vouchers of
G. pyrenaica
and
G.
caucasea
are deposited in the herbarium of the Institute of Botany of the Academy of Sci¬
ences, Tbilisi (TBI). Voucher specimens of
G. germanica
are deposited in the herbarium
of the University Institute of Botany, Innsbruck
(IB).
Methods.
Buds, flowers and fruits at different stages of development were fixed in
FPA50 (formalin, propionic acid,
50%
ethanol,
5:5:
90)
and stored in
70%
ethanol.
Ovules and seeds were dissected out of the ovaries, mounted on microscope slides in
clearing solution according to
Herr
(1971)
and examined with a microscope equipped
with differential interference contrast optics. Mature seeds were cut into slices with a
razor blade before mounting. Photographs were taken with an OLYMPUS
Photomicro¬
graphic
System, using KODAK Technical Pan
135
film at ISO
25
developed in AGFA
Rodinal. For each of the species the lengths and widths of
50
seeds and the lengths of
20
embryos were measured at 100X magnification with an ocular micrometer.
The gynoecia of the investigated species are superior, unilocular, bicarpellate
(very rarely tricarpellate) and paracarpous; they are terminated by a short style and
a 2-lobed stigma. In
Gentiana pyrenaica
the gynophore measures
7-8
mm, in
Gentianella caucasea
and
G. germanica
3-4
mm and
3-5
mm, respectively.
Numerous ovules develop on the parietal placentae along the fused margins of the
carpels.
Gentiana pyrenaica.
The ovule is anatropous, tenuinucellar and unitegmic
(Fig.
2
A). The single integument consists of
8-10
layers of cells and forms a long
micropyle. At the micropylar end the nucellus consists of only one cell layer,
which degenerates during the extension of the embryo sac (Fig.
2
B). As is com¬
mon in
Gentianaceae
(Bouman
&
Schier
1979,
Shamrov
1987),
no vascular bun-
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| Plant systematics and evolution - Comparative embryology of three Ge... (1997) | ||||||||||||||||||||||