of the family Lemnaceae are the smallest flowering plants. They
a distinct group of monocotyledonous plants. Not in without
they are called the most mysterious of the flowering plants on the
Because of their small sizes they sometimes remain elusive from casual
observation. The size of plants does not exceed 1 cm.
duckweeds (Lemna), greater duckweed (Spirodela), and
meal (Wolffia) are frequently encountered by a number in one
Lemnaceae - aquatic, either freely floating or submerged (for
ivy leaf duckweed - Lemna
trisulca), larger partly long-standing (a structly tropical
aequinoctialis, from Africa, is considered as the annual
Lemnaceae - cosmopolitan plants (especially lesser duckweed, Lemna
minor), they extend throughout the entire world, with exception of
hot dry deserts and cold polar regions. About half of the 30
of this family dwell in the tropics and the subtropics, the rest - in
temperate zone. The vegetative body of Lemnaceae according to the
form resembles the tiny floating sheet or the thallus of the lowest
thus for long time they considered to be algae.
No unanimous opinion has been agreed for a word to designate
of these plants. Until now, since it has been called a
a vayey, a shield, a plate, a frond, a listets, a stem or a
In Russia, botanists more frequently is used the term of listets,
in foreign countries - fronds.
The fronds of Lemnaceae grow either singly or connected in
or the networks by the short or elongated legs, formed by the narrow
of the frond (transparent thread) (V.V.Petrov, 1991).
Green fronds of Lemna gibba
thread (waist of listetsa of white color).
Type of the right pocket of Lemna
The shapes of fronds are most diverse: reniform,
elliptical, lancet, linear, globular or oval. The vascular system
in Lemnaceae is practically absent, with exception of Spirodela,
in the roots of which there are tracheids. Roots are absent or
weakly developed (Spirodela) and do not reach down to
They are simple, with a root cap, on one or by beams emerging
the abdominal surface of the fronds and fulfilling mainly functions of
anchors, which prevent the movement of plants in the water. The
part of the frods of Lemna and Spirodela is split by
lateral pockets, in which are embedded the vegetative buds, from which
arise daughter fronds during vegetative multiplication. Sometimes
in one of the pockets a flower bud develops. In the
of other species there is one pocket, and it serves exclusively for the
vegetative multiplication, whereas the flower bud is highly
to 1-2, rarely 3 (in Spirodela) one male and one female flower. A
perianth is absent (I.E.Ivanova, 1971). Male flowers consist of
rarely 2 stamens with size/dimension near 1 mm. The measurement
a stamen is a little more than 1 mm. Bilocular anthers are
to the sealed threads and are supplied with conical pointed svyaznikom.
The ovary is egg-shaped, is monothecal, with 1-6 germs; post
thin/fine, and the stigma is extended in the form of shallow hopper or
cup with the uneven edges.
in the family of Lemnaceae is plotted not in what known for the
plants rhythms, and it was observed so rarely which specially was
In Finland - are noted 33 cases of flowering from 1685-1947, in Poland
- only 2 times with 1679-1959, in America the flowering of Spirodela
in the last 200 years has been observed not more than 20 times.
In Armenia, according to the communication of A.L.
1932 in the lakes of the Loriyakay highland plain they observed a mass
flowering of duckweed.
For the middle strip of Russia within the period from 1814
in published reports appeared only about 25 findings of duckweed
In the ponds along the Volga river it was possible to observe the
flowering of duckweed from 1972 through 1975 (A.L.Takhtadzhan,
In the Krasnodar edge during June 1995 in Krasnodare was noted an
flowering of duckweed in Karasun lake and in the canals of the region
Thapsyg Reservoir, during May 2000 (L.V. Tsatsenko, 2000).
It is possible that the flowering of Lemnaceae is not always
botanists because of the microscopic dimensions of the flowers.
Duckweeds flower in the summer period, usually during June -
sometimes at the end of May or during September. At the beginning
of flowering more or less long chains separate into smaller groups,
of 4-5 fronds in Lemna gibba and of 2-4 fronds in Lemna
Before beginning flowering, morphological conversions of fronds occur
The air chambers increase in Lemna minor, fronds prepared for
increase in the size, and acquire dark green pigmentation.
In Lemna trisulca vegetative fronds are thinned, become pale,
its "top" is bent downward. In Lemna gibba flowering
take on an olive- purple color (A.F.Pantyukh, 1986).
From the moment of the initiation of flowering fronds to the
the process of flowering pass about 20 days. For all Lemnaceae it
is characteristic protogonia, i.e.the stigma of the female flower
ripens first, then stamen of one of the male flowers, and after this
stamen of the second flower. The process of the flowering of
can be represented in the form of the following diagram:
| From the pocket of flowering
fronds first appears
the stamen, which raises itself above the water. In the mouth of
stigma a large watery droplet of nectar then appears that apparently is
used for attracting small insects.
| With a touch, the droplet is
the snout together with any pollen fallen on it. If dusting did
occur, the drop appears again in several hours. The stigma
remains fertile over the course of twenty-four hours. Staurigamia
(cross pollination) occurs during this period.
| The stamens of the second male
flower are advanced
from the pocket of flowering frond 24 h after the appearance of the
The anthers of the stamen of the first flower are closed until the
of the propagation of pollen, and stamen itself descends into the water
and it becomes transparent. The stigma is destroyed at this
and the pollen of the second flower can pollinate only adjacent
| The stamens of the first
about 60 h., the second - 90 h.
| In the beginning in the mature
anthers is revealed
"entomophilous" brilliant yellow pollen, in the form of dense, moist
These clusters are torn off and fall on the surface of the green carpet
of water plants, on which small insects frequently warp (water bulb
mites, aphis). Dusting/pollination occurs with the aid of insects
|For 12-24 h after the anthers open,
the pollen acquires
"anemophilic" appearance - it grows dim, it becomes faded and
friable. At this time it is transferred by airstreams over large
distances. Thus at first Lemnaceae are the
| If cross-pollination did
not occur, then
self-fertilization can occur.
Fruits of duckweeds are well visible with the naked eye,
to the sizes/dimensions they are just larger than a poppy seed.
of plants. Fruits of the family of Lemnaceae are transferred to
large distances on the feet of the swimming and marshy birds.
can also be transported by water. The predominates mode of
in Lemnaceae, however, is colonization by vegetative individuals, since
fruits are formed rarely. Adult plants spread via slowly flowing
water, by frogs and fish, to the bodies of which they stick, but
Many wild wild ducks eat Lemna and Spirodela.
can stick to the paws of birds and are thuy transferred over large