Creating The Charms of Duckweed, An Educational Website
John W. Cross, Ph.D. • Alexandria, VA, USA
The Charms of Duckweed
Providing information about the smallest flowering
plants since 1998.
Hosted by the
Missouri Botanical Garden
http://www.mobot.org/jwcross/duckweed/duckweed.htm
The family of duckweeds (botanically, the Lemnaceae) are the smallest flowering plants. These plants
grow floating in still or slow-moving fresh water around the globe, except in the coldest
regions. The growth of these high-protein plants can be extremely rapid. Lemna is one of the
best known of this group and has been the subject of much research.
Researchers are using these plants to study basic plant development, plant biochemistry,
photosynthesis, the toxicity of hazardous substances, and much more. Genetic engineers are
cloning duckweed genes and modifying duckweeds to inexpensively produce
pharmaceuticals. Environmental scientists are using duckweeds to remove unwanted substances
from water. Aquaculturalists find them an inexpensive feed source for fish farming.
To learn more about these fascinating plants, next read the botanical facts, or view some duckweed
illustrations. Read about cloning….
Copyright © 2013 John W. Cross
Two Themes:
1. People and Events that led me to
create The Charms of Duckweed
2. Helping me keep the website
current and accurate
Two Themes:
1. People and Events that led me to
create The Charms of Duckweed
2. Helping me keep the website
current and accurate
Dr. William S. Hillman (1929– 1981)
Senior Plant Physiologist, Brookhaven National Laboratory, (1962-1981)
Assistant Professor, Yale University,
Ph.D. Yale University
Hillman pioneered basic research on photoperiodic control of flowering in Lemna, “playing a critical role in
the study of photomorphogenesis.” Later, he began collaborating with Bud Culley at LSU on applications of
duckweeds.
Janet P. Slovin, Ph.D.
Molecular Biologist, Research Plant Physiologist,
Genetic Improvement for Fruits and Vegetables
Laboratory, USDA-ARS, Beltsville, MD
“A recognized expert on the Lemnaceae
and on the use of genetic systems to
study plant development.”
Testing Plant Growth Regulators for Phytotoxicity, 1989 - 1994
Dr. William S. Hillman (1929– 1981)
Senior Plant Physiologist, Brookhaven National Laboratory, (1962-1981)
Assistant Professor, Yale University,
Ph.D. Yale University
Hillman pioneered basic research on photoperiodic control of flowering in Lemna, “playing a
critical role in the study of photomorphogenesis.” Late in his life, he began collaborating with
Bud Culley at LSU on applications of duckweeds.
1989 – 1991 / Sogetal Inc., The University of San Francisco
Counting fronds: Exponential growth of duckweed as the basis
of a phytotoxicity bioassay
The average number of fronds per dish is plotted, plus or minus standard
deviation. An exponential curve was fit to the averaged data (see box) and is
plotted (blue line). The average doubling time for frond number ( t2 ) can be
calculated from the exponential constant. In this experiment, t2= ln(2)/0.298 =
2.3 days.
http://www.mobot.org/jwcross/duckweed/Lemna_growth/Lemna_growth.htm
1991 – 1994 / EPL Bio-Analytical Services
Prof. Dr. em. Elias Landolt, 1926 – 2013
1926 Born in Zürich, Switzerland
1945-1949 Study of biology at the Swiss Federal Institute of Technology (ETH) in Zürich
1949 MS at Institut für spezielle Botanik ETH
1953 Ph.D at ETH
1953-1955 Postdoctoral studies at Carnegie Lab., Stanford California and Cal. Tech., Pasadena, California
1955-1964 Assistant and lector at Institut für spezielle Botanik ETH
1964 Prof. of Plant Systematics, Institut für spezielle Botanik ETH
1966-1993 Director of Geobotanical Inst., Rübel Foundation, ETH, and Prof. of Geobotany.
Since 1993 Prof. em. at Geobot. Inst., ETH.
http://geofms.ethz.ch:591/Geodyn/Koordinaten/FMPro?-db=Koordinaten&id=41&-format=datensatzdetail_e.htm&-lay=www&-op=eq&-max=1&-find
Dudley D. Culley, Jr.
Professor Emeritus, School of Renewable Natural Resources.
Louisiana State University
PhD, Mississippi State University.
At a dairy near Baton Rouge, Louisiana, wastes from a milking shed are
washed into a neighboring lagoon planted with duckweed (Spirodela spp.).
The plants can aid in purifying such lagooned wastewaters by absorbing
large quantities of nutrients. In experiments at Louisiana State University
duckweeds are being mixed into poultry, swine, and cattle rations to test
their suitability as feed ingredients. (D. D. Culley, 1976)
From: Ad Hoc Panel of the Advisory Committee on Technology Innovation, Board on Science and Technology for
International Development • Commission. on International Relations, Making Aquatic Weeds Useful: Some
Perspectives for Developing Countries, National Academy of Sciences, Washington, 1976, p. 151.
Figure 2. William S. Hillman and Dudley D. Culley, Jr., 1978
A duckweed/dairy farm
“A duckweed/dairy farm
Although several uses of duckweed thus seem attractive, none has been fully tested in practice.
To introduce some quantitative elements and illustrate some general aspects of the approach,
we will describe one possible system in some detail. Figure 2 is an artists concept of a
duckweed dairy farm system with an average sized herd of cattle (about 100) encompassing
waste treatment, nutrient recycling an deficient energy utilization. It is based on data obtained
at Louisiana State University and elsewhere over the past few years.”
From Hillman, S., Culley, D.D. (1978) The Uses of Duckweed. American Scientist 66(4):442-451.
Emergence of the World-Wide Web in 1993-1994
Early Web Browsers, NCSA Mosaic and Netscape Navigator
In 1993 Mosaic was developed at the NSF-supported National Center for
Supercomputing Applications (NCSA) at the University of Illinois, UrbanaChampaign. Mosaic was the world's first freely available Web browser that
allowed Web pages to include both graphics and text.
Beginning in the early days of the web, it became customary for scientistusers to have their own web sites or home pages, filled with personal
content. NSF encouraged Program Directors to use this space to create
educational pages. So, while I was at NSF in 1994-1996, I began to learn
the basics of web page design and HTML code.
1994 -1996 National Science Foundation
I began The Charms of Duckweed writing the
web pages directly in HTML code.
1998 – 2001 Universities Space Research Association
The Charms of Duckweed first appeared in 1998 on the
personal space provided by my Internet Service Provider
(ISP). The website moved to the Universities Space
Research Association in 1999. Since 2001, it has been
hosted by the Missouri Botanical Garden.
Wayne Armstrong
Palomar College
Botanical Consultant for the Palomar College
Arboretum and editor of the Friend's of the Palomar
College Arboretum Newsletter
Ventral view of Landoltia punctata showing conspicuous
reddish underside and multiple (2-3) roots on each plant.
Cheryl C. Smart Fleming
University of Edinburgh,
Swiss Federal Institute of Technology
Turions and mother fronds of Spirodela polyrrhiza
Ludmila V. Tsatsenko
Doctor of Biological Sciences, Professor
Department of Genetics, Breeding and Seed
Kuban State Agrarian University, Russia
http://www.kubagro.ru/chairs/genetic/staff.php
Two Themes:
1. People and Events that led me to
create The Charms of Duckweed
2. Helping me keep the website
current and accurate
In summary,
acknowledgment and
appreciation go to
these duckweed
pioneers who have
provided images
content or other
assistance to The
Charms of Duckweed
Wayne P. Armstrong, Palomar College
Philomena Chu, Rutgers Univ.
Dudley D. (Bud) Culley, Louisiana State Univ.
Anne H. Datko, NIH/NIMH
Patrick Denny, IHE, Delft
Alberto Godoy, Panama City, Panama
Tim Journey, Aquasanitation
Louis Landesman, Virginia State Univ.
People
Elias Landolt , ETH
Luis Sala, Costa Brava Water Agency, Spain
Paul Skillikorn, Prism, Biotechnology Research and
Development, LLC
Janet P. Slovin, USDA/ARS
Cheryl C. Smart Fleming , University of Edinburgh, ETH
Ludmila V. Tsatsenko, Kuban State Agrarian University
Institutions
The Missouri Botanical Garden
Universities Space Research Association