Duckweed in full bloom
 Close-up
of flowering Lemna gibba.
Lemna flowers consist of two stamens
(pollen
bearing organs) and a single style (pollen receptive
organ).
This plant has two leaves and a single root extending at the
bottom
of the picture. The flower is at the top of the
photograph.
It consists of two stamens (pollen bearing organs) and a
single style (pollen receptive organ). At its top,
each stamen bears an anther where the pollen develops. The
stigma, which will receive the pollen in fertilization, is the
cup-shaped
body atop the stigma. The ovary is at the base of the style.
Read more about flowering
and dormancy in duckweeds and the world's
smallest fruit.
Photo from Wayne Armstrong's Web site, Key
to the Lemnaceae Of North America.
|
Although duckweeds can set seed and produce fruit like other
flowering
plants, they mostly reproduce vegetatively. The
leaves
of duckweeds commonly are called fronds,
but are not considered fronds by strict botanical definition.
Unlike
the ordinary leaves of most plants, each duckweed frond contains buds
from
which more fronds may grow. These buds are hidden from view in
pouches
along the center axis of older fronds. As they grow, new fronds
emerge
through slits in the side of their parent fronds. Until they
mature,
daughter fronds may remain attached to the parent frond. See and read
more
on duckweed anatomy.
A
Formal Botanical Description in industrial-strength
botanical
language is available by L. Watson and M.J. Dallwitz. [
Alternative
Server ]
"Habit and leaf form. Much reduced, aquatic herbs. Plants of very
peculiar vegetative form; thalloid (thallus small to minute, globular,
flat or linear, with or without raphides). Leaves absent.
Plants
with roots, or rootless. Annual. Hydrophytic; free floating."
[ view
accompanying drawings ] (Wolffia, Lemna minor
and
Lemna
trisulca. Note that the species labeled Grantia
microscopica
is likely a synonym for Wolffia
microscopica.)
Another
formal description from a course, Taxonomy of Vascular Plants,
at Cornell University.
Botanical
drawings from "Flora von Deutschland Österreich und der
Schweiz"
by Prof. Dr. Otto Wilhelm Thomé, 1885, reprinted by Kurt
Stüber,
Max-Planck-Institut für Züchtungsforschung, Cologne, Germany.
Taxonomy.
The
Lemnaceae (Duckweed Family), Simplified Key adapted from Wayne P.
Armstrong's
Key
to the Lemnaceae of Western North America. The links
on the right side of the table describe each species in pictures.
Note: the page with pictures may load slowly.
Plant body (frond) has one or more roots.
(click on link for drawings and photos) |
| One root: |
Lemna |
| Two or more roots: |
Spirodela and Landoltia |
| Plant body has no roots |
| Flattened plant body: |
Wolffiella |
| Oval-shaped plant body, less than 1 mm: |
Wolffia |
|
|
Left:
Three duckweeds together: Spirodela (largest),
Lemna
(mid-sized) and Wolffia (smallest), scale in
millimeters.
|
|
Another picture
comparing
different duckweeds from the University of Florida, Center for
Aquatic
and Invasive Plants.
Duckweed
Evolution:
Where did the duckweeds come from? How are the different species
related?
Recent Taxonomic Research (not
available on-line).
Les, D.H., Landolt, E., Crawford, D.J.
(1997)
Systematics
of the Lemnaceae (Duckweeds): inferences from micromolecular and
morphological
data. Plant Systematics and Evolution 204: 161-177.
Les, D. H. & D. J. Crawford. (1999) "Landoltia
(Lemnaceae),
a new genus of duckweeds." Novon 9: 530-533.
Les, Donald H., Crawford, Daniel J., Landolt,
Elias, Gabel,
John D., Kimball, Rebecca T. (2002) "Phylogeny and Systematics of
Lemnaceae,
the Duckweed Family" Systematic Botany 27: 221-240.
Learn more firsthand. If you are
interested
in duckweeds, try some experiments
yourself. They are easily grown
in small containers outside or in the laboratory.
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Last revised: August 5, 2006
