''Wolffia'' is a genus of aquatic plants with a

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

. They include the smallest

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s on Earth. Commonly called watermeal or rootless duckweed, these

aquatic plant Aquatic plants, also referred to as hydrophytes, are vascular plants and Non-vascular plant, non-vascular plants that have adapted to live in aquatic ecosystem, aquatic environments (marine ecosystem, saltwater or freshwater ecosystem, freshwater ...

s resemble specks of

cornmeal Maize meal is a meal (coarse flour) ground from dried maize. It is a common staple food and is ground to coarse, medium, and fine consistencies, but it is not as fine as wheat flour can be.Herbst, Sharon, ''Food Lover's Companion'', Third Editi ...

floating on the water. They often float together in pairs or form floating mats with related plants, such as ''

Lemna ''Lemna'' is a genus of free-floating aquatic plants referred to by the common name "duckweed". They are morphologically divergent members of the arum family Araceae. These rapidly growing plants have found uses as a model system for studies in ...

'' and ''

Spirodela ''Spirodela'' is a genus of aquatic plants, one of several genera containing plants commonly called duckweed. ''Spirodela'' species are members of the Araceae under the APG II system. They were formerly members of the Lemnaceae. Description ' ...

'' species.

Description

''Wolffia'' are free-floating aquatic plants with

frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

s that are nearly spherical to cylindrical in shape and lack airspaces or veins. They do not have roots. Their rarely seen flowers originate from a cavity on the upper surface of the frond, and each flower has one stamen and one pistil. Although ''Wolffia'' can reproduce by seed, they usually use

vegetative reproduction Vegetative reproduction (also known as vegetative propagation, vegetative multiplication or cloning) is a form of asexual reproduction occurring in plants in which a new plant grows from a fragment or cutting of the parent plant or specializ ...

. A mother frond has a terminal conical cavity from which it produces daughter fronds.

Physiology

The growth rate of ''Wolffia'' varies within and among species. The rates of

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

and

respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...

also vary proportionately to growth rate. The fastest growth rate (in fact, the fastest growth rate of any

) is shown by a clone of ''Wolffia microscopica'', with a

doubling time The doubling time is the time it takes for a population to double in size/value. It is applied to population growth, inflation, resource extraction, consumption of goods, compound interest, the volume of malignant tumours, and many other things t ...

of 29.3 hours.

As food

''Wolffia'' are a potential high-protein livestock food source. One species, ''W. microscopica'', is over 20%

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

by dry weight and has high content of

essential amino acid An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life forms ...

s. They have historically been collected from the water and eaten as a vegetable in Asia.

Species

, eleven species are accepted on

Kew Kew () is a district in the London Borough of Richmond upon Thames. Its population at the 2011 census was 11,436. Kew is the location of the Royal Botanic Gardens ("Kew Gardens"), now a World Heritage Site, which includes Kew Palace. Kew is ...

Plants of the World Online Plants of the World Online (POWO) is an online taxonomic database published by the Royal Botanic Gardens, Kew. History Following the Convention on Biological Diversity, the Royal Botanic Gardens in Kew launched Plants of the World Online i ...

: *'' Wolffia angusta'' *'' Wolffia arrhiza'' *'' Wolffia australiana'' *'' Wolffia borealis'' *'' Wolffia brasiliensis'' *'' Wolffia columbiana'' *'' Wolffia cylindracea'' *''

Wolffia elongata ''Wolffia'' is a genus of aquatic plants with a cosmopolitan distribution. They include the smallest flowering plants on Earth. Commonly called watermeal or rootless duckweed, these aquatic plants resemble specks of cornmeal floating on the wat ...

'' *'' Wolffia globosa'' *'' Wolffia microscopica'' *'' Wolffia neglecta''

References

External links

The Duckweed Genome Project
from

Rutgers University Rutgers University ( ), officially Rutgers, The State University of New Jersey, is a Public university, public land-grant research university consisting of three campuses in New Jersey. Chartered in 1766, Rutgers was originally called Queen's C ...

* *Landolt, E. (1986) Biosystematic investigations in the family of duckweeds (Lemnaceae). Vol. 2. The family of Lemnaceae - A monographic study. Part 1 of the monograph: Morphology; karyology; ecology; geographic distribution; systematic position; nomenclature; descriptions. Veröff. Geobot. Inst., Stiftung Rübel, ETH, Zurich. {{Taxonbar, from=Q163015 Lemnoideae Araceae genera Freshwater plants