Wolffia arrhiza
Encyclopedia
Wolffia arrhiza is a species of flowering plant known by the common names spotless watermeal and rootless duckweed, belonging to the Araceae
, a family rich in water-loving species, such as Arum
and Pistia
. It is the smallest vascular plant
on Earth. It is native to Europe, Africa, and parts of Asia, and it is present in other parts of the world as a naturalized species
. It is an aquatic plant
which grows in quiet water bodies such as ponds. The green part of the plant, the frond, is a sphere measuring approximately one millimeter wide but with a flat top that floats at the water's surface. It has a few parallel rows of stoma
ta. There is no root. The plant produces a minute flower fully equipped with one stamen
and one pistil
. It often multiplies by vegetative reproduction
, however, with the rounded part budding off into a new individual. In cooler conditions the plant becomes dormant and sinks to the bed of the water body to overwinter as a turion. The plant is a mixotroph
which can produce its own energy via photosynthesis
or absorb it from the environment in the form of dissolved carbon
.
This tiny plant is a nutritious food. Its green part is about 40% protein by dry weight
and its turion is about 40% starch
. It contains many amino acid
s important to the human diet, relatively large amounts of dietary mineral
s and trace elements such as calcium
, magnesium
, and zinc
, and vitamin B12
. It has long been used as a cheap food source in Burma, Laos
, and Thailand
, where it is known as khai-nam ("eggs of the water"). The plant is prolific in its reproduction, growing in floating mats that can be harvested every 3 to 4 days; it has been shown to double its population in less than four days in vitro
.
It is also useful as a form of agricultural
and municipal water treatment
. It is placed in effluent
from black tiger shrimp
farms
to absorb and metabolize pollutants. The plants grow quickly and take up large amounts of nitrogen
and phosphorus
from the water. The plants that grow in the wastewater can then be used as feed
for animals, such as carp
, Nile tilapia
, and chicken
s.
Araceae
Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe or leaf-like bract. Also known as the Arum family, members are often colloquially...
, a family rich in water-loving species, such as Arum
Arum
Arum is a genus of about 25 species of flowering plants in the family Araceae, native to Europe, northern Africa, and western Asia, with the highest species diversity in the Mediterranean region....
and Pistia
Pistia
Pistia is a genus of aquatic plant in the arum family, Araceae. The single species it comprises, Pistia stratiotes, is often called water cabbage, water lettuce, or Nile cabbage. Its native distribution is uncertain, but probably pantropical; it was first described from the Nile near Lake Victoria...
. It is the smallest vascular plant
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
on Earth. It is native to Europe, Africa, and parts of Asia, and it is present in other parts of the world as a naturalized species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
. It is an aquatic plant
Aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...
which grows in quiet water bodies such as ponds. The green part of the plant, the frond, is a sphere measuring approximately one millimeter wide but with a flat top that floats at the water's surface. It has a few parallel rows of stoma
Stoma
In botany, a stoma is a pore, found in the leaf and stem epidermis that is used forgas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the opening...
ta. There is no root. The plant produces a minute flower fully equipped with one stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
and one pistil
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
. It often multiplies by vegetative reproduction
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...
, however, with the rounded part budding off into a new individual. In cooler conditions the plant becomes dormant and sinks to the bed of the water body to overwinter as a turion. The plant is a mixotroph
Mixotroph
A mixotroph is a microorganism that can use a mix of different sources of energy and carbon. Possible are alternations between photo- and chemotrophy, between litho- and organotrophy, between auto- and heterotrophy or a combination of it...
which can produce its own energy via photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
or absorb it from the environment in the form of dissolved carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
.
This tiny plant is a nutritious food. Its green part is about 40% protein by dry weight
Dry matter
The dry matter is a measurement of the mass of something when completely dried.The dry matter of plant and animal material would be its solids, i.e. all its constituents excluding water. The dry matter of food would include carbohydrates, fats, proteins, vitamins, minerals, and antioxidants...
and its turion is about 40% starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
. It contains many amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s important to the human diet, relatively large amounts of dietary mineral
Dietary mineral
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...
s and trace elements such as calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, and zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, and vitamin B12
Vitamin B12
Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
. It has long been used as a cheap food source in Burma, Laos
Laos
Laos Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ Sathalanalat Paxathipatai Paxaxon Lao, officially the Lao People's Democratic Republic, is a landlocked country in Southeast Asia, bordered by Burma and China to the northwest, Vietnam to the east, Cambodia to the south and Thailand to the west...
, and Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
, where it is known as khai-nam ("eggs of the water"). The plant is prolific in its reproduction, growing in floating mats that can be harvested every 3 to 4 days; it has been shown to double its population in less than four days in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
.
It is also useful as a form of agricultural
Agricultural wastewater treatment
Agricultural wastewater treatment relates to the treatment of wastewaters produced in the course of agricultural activities. Agriculture is a highly intensified industry in many parts of the world, producing a range of wastewaters requiring a variety of treatment technologies and management...
and municipal water treatment
Sewage
Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...
. It is placed in effluent
Effluent
Effluent is an outflowing of water or gas from a natural body of water, or from a human-made structure.Effluent is defined by the United States Environmental Protection Agency as “wastewater - treated or untreated - that flows out of a treatment plant, sewer, or industrial outfall. Generally refers...
from black tiger shrimp
Penaeus monodon
Penaeus monodon, the giant tiger prawn , is a marine crustacean that is widely reared for food.-Distribution:...
farms
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
to absorb and metabolize pollutants. The plants grow quickly and take up large amounts of nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
from the water. The plants that grow in the wastewater can then be used as feed
Compound feed
Compound feeds are feedstuffs that are blended from various raw materials and additives. These blends are formulated according to the specific requirements of the target animal...
for animals, such as carp
Carp
Carp are various species of oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. The cypriniformes are traditionally grouped with the Characiformes, Siluriformes and Gymnotiformes to create the superorder Ostariophysi, since these groups have certain...
, Nile tilapia
Oreochromis niloticus
The Nile Tilapia, Oreochromis niloticus is a relatively large cichlid fish, which is native to Africa from Egypt south to East and Central Africa, and as far west as Gambia. It is also native to Israel, and numerous introduced populations exist outside its natural range.It is also commercially...
, and chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...
s.