2. Lemna, common duckweeds.	3. Spirodela & Landoltia, the giant duckweeds
A drawing of Lemna minor.  This drawing shows vegetative plants.  Each new leaf emerges from a cleft or scale in the margin of the last leaf.  Rapidly growing plants often have three or four attached fronds, rather than the one or two fronds shown. Lemna trisulca (Ivy-leaf duckweed) may have many full-grown fronds attached together.	A drawing of Spirodela polyrhiza.  Spirodela species are the largest and least simplified of the Lemnaceae. Originally Spirodela was named Lemna major before being placed in a separate genus. Recently, S. punctata a species intermediate between Lemna and Spirodela was renamed Landoltia punctata. Each Spirodela plant has several roots that may become tangled with those of other plants.  The rootcap may be quite prominent.  Scale bar = 5 mm.
Lemna gibba seen from above.  There are two mature fronds and two emerging daughter fronds.  A single root can be seen at the top of the photo.  Photo from the work of Elias Landolt (1986), Biosystematic Investigations in the family of duckweeds (Lemnaceae) vol. 2, p.515.  Photo used with permission.	Spirodela polyrhiza seen from above (left) and below (right).  Each small mark is one millimeter.  The lower side is dark from anthocyanin pigments, the same pigment family that gives red roses and grapes their color.  The ridges along the length of the fronds are called nervi.  Link for more information and photos of Spirodela. Photo  from USGS Northern Prairie Wildlife Research Center, Jamestown, North Dakota.
Lemna gibba seen from the side.  The species name, gibba refers to the enlarged air pockets, called aerenchyma. Photo from Wayne Armstrong's Web site, Key to the Lemnaceae Of North America. Lemna trisulca [ photo ] is flattened and grows submerged as a network of fronds.  More photos.	Landoltia (Spirodela) punctata. This side view shows the underside, with red anthocyanin pigment and several (2-3) roots extending from each plant.  Link for more information and photos of Landoltia. Photo from Wayne Armstrong's Web site, Key to the Lemnaceae Of North America.

4. Wolffiella	5. Wolffia, the smallest flowering plants.
A clump of Wolffiella gladiata floating just below the water surface. Fronds grow submerged except when flowering or fruiting. Photo from the work of Elias Landolt (1986), Biosystematic Investigations in the family of duckweeds (Lemnaceae) vol. 2, p.523.  Photo used with permission.	Wolffia arrhiza seen from above. Wolffia floats on the surface and have no roots.  They are often called watermeal because without a microscope they look like dots of cornmeal.  View the tiny flower.  Link for information and photos of Florida's Wolffia columbiana. Photo from the work of Elias Landolt (1986), Biosystematic Investigations in the family of duckweeds (Lemnaceae) vol. 2, p.527.  Photo used with permission.

6. Micrographs:

An Emerging Frond of Spirodela.

[ Click for a high-resolution image. ]
New fronds of Lemna and Spirodela emerge from a pocket cleft towards the base of the mother frond.  This image is a cross-sectional composite made from many light micrographs.  The image does not include the the mother frond, except at the base where mother and daughter are still connected.  In the mid-zone, the air pockets (aerenchyma) are beginning to develop.  The calibration line (lower left) is 100 µm.  The overal length of this frond is 1.28 mm.

This image is from the Ph.D. thesis (Developmental and Molecular Aspects of Turion Formation in Spirodela polyrrhiza and its Induction by Abscisic Acid, 1992, University of Edinburgh, Scotland) of Cheryl C. Smart, currently at the ETH, Zurch, Switzerland.  It was sent courtesy of Dr. A.T. Trewavas.  I have electronically adjusted the background density to reduce the mosaic appearance of the composite.

Wolffia Ultrastructure:

White, S.L. and R.R. Wise. 1998. Anatomy and ultrastructure of Wolffia columbiana and W. borealis (Lemnaceae). International Journal of Plant Sciences, 159: 297-304. (not available on-line).

7. Links for Duckweed Photos and Illustrations.
 

Duckweed anatomy:  Illustrations from the work of Elias Landolt, including diagrams of the hidden growth points of the plant.
Photographs of many duckweed species can be found on Wayne P. Armstrong's Key To The Lemnaceae Of North America.
Beautiful, detailed color photographs of duckweeds in Lemnaceae - bioindicators for the ecosystem by Ludmila V. Tsatsenko and N.G. Malyuga, Kuban State Agicultural University, Krasnodar, Russia.  Professor Tsatsenko's sharp photos include all phases of the life cycle.  In addition, there is much information on the use of duckweed bioassays as bioindicators for studies in ecology and agriculture, and information on other uses for these plants.	Lemna gibba

More drawings of duckweed species (Lemna minor L., Lemna gibba L., Lemna trisulca L. and Spirodela polyrrhiza Schleid) by Swedish botanist Carl Axel Magnus Lindman (1856 - 1928) from his Bilder ur Nordens Flora.

Drawing of Lemna aequinoctialis Welw, from Manual de las Plantas de Costa Rica, which includes a section on Lemnaceae.

Florida's Native Duckweeds, Spirodela, Lemna, Wolffiella and Wolffia, from the University of Florida, Center for Aquatic and Invasive Plants.

Excellent photos (with text in Swedish) from Naturhistoriska riksmuseet, Stockholm:
Spirodela polyrhiza, L. gibba, and Lemna trisulca.  Other species are described, but without photos.

Do you want to see for yourself?  Link to:  Experiments and Projects with Duckweed
 
 
 
 

Last revised:  August 5, 2006