Aquatic plants are

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

s that have adapted to living in aquatic environments (

saltwater Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

). They are also referred to as hydrophytes or macrophytes to distinguish them from

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

and other microphytes. A macrophyte is a plant that grows in or near water and is either emergent, submergent, or floating. In lakes and rivers macrophytes provide cover for

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

, substrate for aquatic

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s, produce

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

, and act as food for some fish and wildlife. Macrophytes are primary producers and are the basis of the food web for many organisms. They have a significant effect on soil chemistry and light levels as they slow down the flow of water and capture pollutants and trap sediments. Excess sediment will settle into the benthos aided by the reduction of flow rates caused by the presence of plant stems, leaves and roots. Some plants have the capability of absorbing pollutants into their tissue.

Seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

s are multicellular

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

and, although their ecological impact is similar to other larger water plants, they are not typically referred to as macrophytes. Aquatic plants require special adaptations for living submerged in

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

, or at the water's surface. The most common adaptation is the presence of lightweight internal packing cells,

aerenchyma Aerenchyma or aeriferous parenchyma or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and t ...

, but floating leaves and finely dissected leaves are also common.Sculthorpe, C. D. 1967. The Biology of Aquatic Vascular Plants. Reprinted 1985 Edward Arnold, by London.Hutchinson, G. E. 1975. A Treatise on Limnology, Vol. 3, Limnological Botany. New York: John Wiley. Aquatic plants can only grow in water or in

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

that is frequently saturated with water. They are therefore a common component of wetlands.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. One of the largest aquatic plants in the world is the Amazon water lily; one of the smallest is the minute

duckweed Lemnoideae is a subfamily of flowering aquatic plants, known as duckweeds, water lentils, or water lenses. They float on or just beneath the surface of still or slow-moving bodies of fresh water and wetlands. Also known as bayroot, they arose ...

. Many small aquatic animals use plants such as duckweed for a home, or for protection from predators. Some other familiar examples of aquatic plants include

floating heart ''Nymphoides'', or floatingheart, is a genus of aquatic flowering plants in the family Menyanthaceae. The genus name refers to their resemblance to the water lily ''Nymphaea''. ''Nymphoides'' are aquatic plants with submerged roots and floating L ...

, water lily, lotus, and

water hyacinth ''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth is an aquatic plant native to South America, naturalized throughout the world, and often invasive outside its native range.

Distribution

The principal factor controlling the distribution of aquatic plants is the availability of water. However, other factors may also control their distribution including nutrient availability, disturbance from waves, grazing, and salinity. Some aquatic plants are able to thrive in brackish, saline, and salt water.

Evolution

Aquatic plants have adapted to live in either freshwater or saltwater. Aquatic

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...

s have originated on multiple occasions in different plant families; they can be

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

s or angiosperms (including both

monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...

s and

dicot The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...

s). The only

angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

capable of growing completely submerged in seawater are the

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...

es. Examples are found in genera such as '' Thalassia'' and ''

Zostera ''Zostera'' is a small genus of widely distributed seagrasses, commonly called marine eelgrass, or simply seagrass or eelgrass, and also known as seaweed by some fishermen and recreational boaters including yachtsmen. The genus ''Zostera'' con ...

''. An aquatic origin of angiosperms is supported by the evidence that several of the earliest known fossil angiosperms were aquatic. Aquatic plants are phylogenetically well dispersed across the angiosperms, with at least 50 independent origins, although they comprise less than 2% of the angiosperm species. Archaefructus represents one of the oldest, most complete angiosperm fossils which is around 125 million years old. These plants require special adaptations for living submerged in water or floating at the surface.

Aquatic adaptation

Reproduction

Although most aquatic

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s can reproduce by flowering and setting seeds, many have also evolved to have extensive asexual reproduction by means of

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

s, turions, and fragments in general.

Photosynthesis

Submerged aquatic plants have more restricted access to carbon as carbon dioxide compared to terrestrial plants. They may also experience reduced light levels. The diffuse

boundary layer In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary condi ...

s (DBLs) around submerged leaves and photosynthetic stems. Aquatic plants have DBLs that vary based on the leaves' thickness, shape and density and they are the main factor responsible for the greatly reduced rate of gaseous transport across the leaf/water boundary and therefore greatly inhibit transport of carbon dioxide transport. To overcome this limitation, many aquatic plants have evolved to metabolise bicarbonate ions as a source of carbon. Environmental variables affect the instantaneous photosynthetic rates of aquatic plants and the photosynthetic enzymes pigments. In water, light intensity rapidly decreases with depth. Respiration is also higher in the dark per the unit volume of the medium they live in.

Morphology

Fully submerged aquatic plants have little need for stiff or woody tissue as they are able to maintain their position in the water using buoyancy typically from gas filled lacunaa or turgid

Aerenchyma Aerenchyma or aeriferous parenchyma or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and t ...

cells. When removed from the water, such plants are typically limp and loose

turgor Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall. It is also called ''hydrostatic pressure'', and is defined as the pressure in a fluid measured at a certain point within itself when at equilibriu ...

rapidly. Those living in rivers do, however, need sufficient structural

xylem Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...

to avoid being damaged by fast flowing water and they also need strong mechanisms of attachment to avoid being uprooted by river flow. Many fully submerged plants have finely dissected leaves, probably to reduce drag in rivers and to provide a much increased surface area for interchange of minerals and gasses. Some species of plants such as ''

Ranunculus aquatilis ''Ranunculus aquatilis'', the common water-crowfoot or white water-crowfoot, is a plant species of the genus ''Ranunculus'', native throughout most of Europe and western North America, and also northwest Africa. This is an aquatic plant Aqua ...

'' have two different leaf forms with finely dissected leaves that are fully submerged and entire leaves on the surface of the water. Some still-water plants can alter their position in the water column at different seasons. One notable example is ''

Water soldier ''Stratiotes'' is a genus of submerged aquatic plant commonly known as water soldiers, described as a genus by Linnaeus in 1753. Several specific names have been coined within the genus, but at present only one is recognized: ''Stratiotes aloid ...

'' which rests as a rootless rosette on the bottom of the water body but slowly floats to the surface in late Spring so that its inflorescence can emerge into the air. While it is ascending through the water column it produces roots and vegetative daughter plants by means of

rhizomes In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

. When flowering is complete, the plant descends through the water column and the roots atrophy. In floating aquatic angiosperms, the leaves have evolved to only have

stoma In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

ta on the top surface to make use of atmospheric carbon dioxide. Gas exchange primarily occurs through the top surface of the leaf due to the position of the stomata, and the stomata are in a permanently open state. Due to their aquatic surroundings, the plants are not at risk of losing water through the stomata and therefore face no risk of dehydration. For carbon fixation, some aquatic angiosperms are able to uptake CO₂ from

bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemic ...

in the water, a trait that does not exist in terrestrial plants. Angiosperms that use - can keep levels satisfactory, even in basic environments with low carbon levels.

Buoyancy

Due to their environment, aquatic plants experience buoyancy which counteracts their weight. Because of this, their cell covering are far more flexible and soft, due to a lack of pressure that terrestrial plants experience. Green algae are also known to have extremely thin cell walls due to their aquatic surroundings, and research has shown that green algae is the closest ancestor to living terrestrial and aquatic plants. Terrestrial plants have rigid cell walls meant for withstanding harsh weather, as well as keeping the plant upright as the plant resists gravity. Gravitropism, along with phototropism and hydrotropism, are traits believed to have evolved during the transition from an aquatic to terrestrial habitat. Terrestrial plants no longer had unlimited access to water and had to evolve to search for nutrients in their new surroundings as well as develop cells with new sensory functions, such as

statocyte Statocytes are gravity-sensing ( gravitropic) cells in higher plants. They contain amyloplasts-statoliths – starch-filled amyloplastic organelles – which sediment at the lowest part of the cells. Statocytes are present in the elongating region o ...

Terrestrial plants in aquatic environments

Terrestrial plants may undergo physiological changes when submerged due to flooding. When submerged, new leaf growth has been found to have thinner leaves and thinner cell walls than the leaves on the plant that grew while above water, along with oxygen levels being higher in the portion of the plant grown underwater versus the sections that grew in their terrestrial environment. This is considered a form of

phenotypic plasticity Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompa ...

as the plant, once submerged, experiences changes in morphology better suited to their new aquatic environment. However, while some terrestrial plants may be able to adapt in the short-term to an aquatic habitat, it may not be possible to reproduce underwater, especially if the plant usually relies on terrestrial

pollinator A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains. Insects are the maj ...

Classification of macrophytes

Based on growth form, macrophytes can be characterised as: * Emergent * Submerged **Rooted: rooted to the substrate **Unrooted: free-floating in the water column **Attached: attached to substrate but not by roots * Floating-leaved *Free-floating

Emergent

An emergent plant is one which grows in water but pierces the surface so that it is partially exposed to air. Collectively, such plants are emergent vegetation. This habit may have developed because the leaves can

photosynthesize Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

more efficiently in air and competition from submerged plants but often, the main aerial feature is the flower and the related reproductive process. The emergent habit permits pollination by wind or by flying

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s. There are many species of emergent plants, among them, the reed (''

Phragmites ''Phragmites'' () is a genus of four species of large perennial reed grasses found in wetlands throughout temperate and tropical regions of the world. Taxonomy The World Checklist of Selected Plant Families, maintained by Kew Garden in London ...

''), ''

Cyperus papyrus ''Cyperus papyrus'', better known by the common names papyrus, papyrus sedge, paper reed, Indian matting plant, or Nile grass, is a species of aquatic flowering plant belonging to the sedge family Cyperaceae. It is a tender herbaceous perenn ...

'', ''

Typha ''Typha'' is a genus of about 30 species of monocotyledonous flowering plants in the family Typhaceae. These plants have a variety of common names, in British English as bulrush or reedmace, in American English as reed, cattail, or punks, in A ...

'' species,

flowering rush ''Butomus'' is the only known genus in the plant family Butomaceae, native to Europe and Asia. It is considered invasive in some parts of the United States. Taxonomy The Butomaceae family has been recognized by most taxonomists as a plant ...

and

wild rice Wild rice, also called manoomin, Canada rice, Indian rice, or water oats, is any of four species of grasses that form the genus ''Zizania'', and the grain that can be harvested from them. The grain was historically gathered and eaten in both ...

species. Some species, such as

purple loosestrife ''Lythrum salicaria'' or purple loosestrifeFlora of NW Europe''Lythrum salicaria'' is a flowering plant belonging to the family Lythraceae. It should not be confused with other plants sharing the name loosestrife that are members of the family P ...

, may grow in water as emergent plants but they are capable of flourishing in fens or simply in damp ground.

Submerged

Submerged macrophytes completely grow under water with roots attached to the substrate (e.g. ''

Myriophyllum spicatum ''Myriophyllum spicatum'' (Eurasian watermilfoil or spiked water-milfoil) is native to Europe, Asia, and north Africa, but has a wide geographic and climatic distribution among some 57 countries, extending from northern Canada to South Africa. It ...

'') or without any root system (e.g. ''

Ceratophyllum demersum ''Ceratophyllum demersum'', commonly known as hornwort, rigid hornwort, coontail, or coon's tail, is a species of ''Ceratophyllum''. It is a submerged, free-floating aquatic plant, with a cosmopolitan distribution, native to all continents except ...

''). Helophytes are plants that grows in a

marsh A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found at ...

, partly submerged in water, so that it regrows from

bud In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be spec ...

s below the water surface. Fringing stands of tall vegetation by water basins and rivers may include helophytes. Examples include stands of ''

Equisetum fluviatile ''Equisetum fluviatile'', the water horsetail or swamp horsetail, is a vascular plant that commonly grows in dense colonies along freshwater shorelines or in shallow water in ponds, swamps, ditches, and other sluggish or still waters with mud bo ...

'', ''

Glyceria maxima ''Glyceria maxima'' (syn. ''G. aquatica'' (L.) Wahlenb.; ''G. spectabilis'' Mert. & W.D.J. Koch; ''Molinia maxima'' Hartm.; ''Poa aquatica'' L.), commonly known as great manna grass, reed mannagrass, reed sweet-grass, and greater sweet-grass is a ...

'', ''

Hippuris vulgaris ''Hippuris vulgaris'' (from Greek: ἵππος — ''horse'' and οὐρά — ''tail''), known as mare's-tail or common mare's-tail, is a common aquatic plant of Eurasia and North America ranging from Greenland to the Tibetan Plateau to Arizon ...

'', ''

Sagittaria ''Sagittaria'' is a genus of about 303. Sagittaria Linnaeus
''Flora of North ...

'', ''

Carex ''Carex'' is a vast genus of more than 2,000 species of grass-like plants in the family Cyperaceae, commonly known as sedges (or seg, in older books). Other members of the family Cyperaceae are also called sedges, however those of genus ''Carex'' ...

'', ''

Schoenoplectus ''Schoenoplectus'' (club-rush ld World species bulrush or tule ew World species is a genus of plants in the sedges with a cosmopolitan distribution. Note that the name bulrush is also applied to species in the unrelated genus ''Typha'' as well ...

'', ''

Sparganium ''Sparganium'' (bur-reed) is a genus of flowering plants, described as a genus by Linnaeus in 1753. It is widespread in wet areas in temperate regions of both the Northern and Southern Hemispheres. The plants are perennial marsh plants that c ...

'', ''

Acorus ''Acorus'' is a genus of monocot flowering plants. This genus was once placed within the family Araceae (aroids), but more recent classifications place it in its own family Acoraceae and order Acorales, of which it is the sole genus of the oldes ...

'', yellow flag (''

Iris pseudacorus ''Iris pseudacorus'', the yellow flag, yellow iris, or water flag, is a species of flowering plant in the family Iridaceae. It is native to Europe, western Asia and northwest Africa. Its specific epithet ''pseudacorus'' means "false acorus", re ...

''), ''

'' and ''

Phragmites australis ''Phragmites australis'', known as the common reed, is a species of plant. It is a broadly distributed wetland grass that can grow up to tall. Description ''Phragmites australis'' commonly forms extensive stands (known as reed beds), which may ...

''.

Floating-leaved

Floating-leaved macrophytes have root systems attached to the substrate or bottom of the body of water and with leaves that float on the water surface. Common floating leaved macrophytes are water lilies (family

Nymphaeaceae Nymphaeaceae () is a family of flowering plants, commonly called water lilies. They live as rhizomatous aquatic herbs in temperate and tropical climates around the world. The family contains nine genera with about 70 known species. Water li ...

), pondweeds (family

Potamogetonaceae The Potamogetonaceae, commonly referred to as the pondweed family, is an aquatic family of monocotyledonous flowering plants. The roughly 110 known species are divided over six genera. The largest genus in the family by far is ''Potamogeton'', w ...

Free-floating

Free-floating macrophytes are found suspended on water surface with their root not attached to the substrate, sediment, or bottom of the water body. They are easily blown by air and provide breeding ground for mosquitoes. Example include '' Pistia'' spp. commonly called water lettuce, water cabbage or Nile cabbage.

Morphological classification

The many possible classifications of aquatic plants are based upon morphology. One example has six groups as follows: * Amphiphytes: plants that are adapted to live either submerged or on land * Elodeids: stem plants that complete their entire lifecycle submerged, or with only their flowers above the waterline *

Isoetid Isoetids are aquatic plants or wetland plants named for their superficial similarity to the quillworts, ''Isoetes''. They occur in wetlands and on shorelines with low nutrient availability. Owing to their slow growth rates, they are also often fo ...

s: rosette plants that complete their entire lifecycle submerged *

Helophyte Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that g ...

s: plants rooted in the bottom, but with leaves above the waterline * Nymphaeids: plants rooted in the bottom, but with leaves floating on the water surface *

Neuston Neuston, also known as pleuston, are organisms that live at the surface of the ocean or an estuary, or at the surface of a lake, river or pond. Neuston can live on top of the water surface or may be attached to the underside of the water surface. ...

: vascular plants that float freely in the water

Functions of macrophytes in aquatic systems

Macrophytes perform many ecosystem functions in aquatic ecosystems and provide services to human society. One of the important functions performed by macrophyte is uptake of dissolved nutrients including Nitrogen and Phosphorus. Macrophytes are widely used in constructed wetlands around the world to remove excess N and P from polluted water. Beside direct nutrient uptake, macrophytes indirectly influence nutrient cycling, especially N cycling through influencing the denitrifying bacterial functional groups that are inhabiting on roots and shoots of macrophytes. Macrophytes promote the sedimentation of suspended solids by reducing the current velocities, impede erosion by stabilising soil surfaces. Macrophytes also provide spatial heterogeneity in otherwise unstructured water column. Habitat complexity provided by macrophytes tends to increase diversity and density of both fish and invertebrates. The additional site-specific macrophytes' value provides wildlife habitat and makes treatment systems of wastewater aesthetically satisfactory.

Uses and importance to humans

Food crops

Some aquatic plants are used by humans as a food source. Examples include wild rice (''

Zizania Wild rice, also called manoomin, Canada rice, Indian rice, or water oats, is any of four species of grasses that form the genus ''Zizania'', and the grain that can be harvested from them. The grain was historically gathered and eaten in both ...

''), water caltrop (''

Trapa natans The water caltrop is any of three extant species of the genus ''Trapa'': ''Trapa natans'', ''Trapa bicornis'' and the endangered ''Trapa rossica''. It is also known as buffalo nut, bat nut, devil pod, ling gok (Chinese: 菱角), ling nut, lin kok ...

''), Chinese water chestnut (''

Eleocharis dulcis ''Eleocharis dulcis'', the Chinese water chestnut or water chestnut, is a grass-like sedge native to Asia, tropical Africa, and Oceania. It is grown in many countries for its edible corms. The water chestnut is not a nut, but an aquatic ve ...

''), Indian lotus (''

Nelumbo nucifera ''Nelumbo nucifera'', also known as sacred lotus, Laxmi lotus, Indian lotus, or simply lotus, is one of two extant species of aquatic plant in the family Nelumbonaceae. It is sometimes colloquially called a water lily, though this more often re ...

''), water spinach (''

Ipomoea aquatica ''Ipomoea aquatica'', widely known as water spinach, is a semi- aquatic, tropical plant grown as a vegetable for its tender shoots. ''I. aquatica'' is generally believed to have been first domesticated in Southeast Asia. It is widely cultivate ...

''), and watercress (''

Rorippa nasturtium-aquaticum Watercress or yellowcress (''Nasturtium officinale'') is a species of aquatic plant, aquatic flowering plant in the cabbage family Brassicaceae. Watercress is a rapidly growing perennial plant native to Europe and Asia. It is one of the oldest ...

'').

Bioassessment

A decline in a macrophyte community may indicate water quality problems and changes in the ecological status of the water body. Such problems may be the result of excessive

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can ...

herbicides Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

, or

salination Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization. Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the ...

. Conversely, overly high nutrient levels may create an overabundance of macrophytes, which may in turn interfere with

lake processing A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

. Macrophyte levels are easy to sample, do not require laboratory analysis, and are easily used for calculating simple abundance metrics.

Potential sources of therapeutic agents

Phytochemical and pharmacological researches suggest that freshwater macrophytes, such as ''

Centella asiatica ''Centella asiatica'', commonly known as gotu kola, kodavan, Indian pennywort and Asiatic pennywort, is a herbaceous, perennial plant in the flowering plant family Apiaceae. It is native to tropical regions of Africa, Asia, Australia, and islan ...

'', ''

Nasturtium officinale Watercress or yellowcress (''Nasturtium officinale'') is a species of aquatic flowering plant in the cabbage family Brassicaceae. Watercress is a rapidly growing perennial plant native to Europe and Asia. It is one of the oldest known leaf ve ...

'', ''

'' and '' Ludwigia adscendens'', are promising sources of anticancer and antioxidative natural products. Hot water extracts of the stem and root of ''Ludwigia adscendens'', as well as those of the fruit, leaf and stem of ''Monochoria hastata'' were found to have

lipoxygenase Lipoxygenases () are a family of (non-heme) iron-containing enzymes most of which catalyze the dioxygenation of polyunsaturated fatty acids in lipids containing a cis,cis-1,4- pentadiene into cell signaling agents that serve diverse roles as auto ...

inhibitory activity. Hot water extract prepared from the leaf of ''Ludwigia adscendens'' exhibits

alpha-glucosidase α-Glucosidase (EC 3.2.1.20, maltase, glucoinvertase, glucosidosucrase, maltase-glucoamylase, α-glucopyranosidase, glucosidoinvertase, α-D-glucosidase, α-glucoside hydrolase, α-1,4-glucosidase, α-D-glucoside glucohydrolase; systematic n ...

inhibitory activity more potent than that of

acarbose Acarbose (INN) is an anti-diabetic drug used to treat diabetes mellitus type 2 and, in some countries, prediabetes. It is a generic sold in Europe and China as Glucobay (Bayer AG), in North America as Precose (Bayer Pharmaceuticals), and in Cana ...

Wastewater treatment

Macrophytes have an essential role in some forms of wastewater treatment, most commonly in small scale

sewage treatment Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding envir ...

using

constructed wetlands A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. ...

or in polishing lagoons for larger schemes.

Invasive aquatic plants

The introduction of non-native aquatic plants has resulted in numerous examples across the world of such plants becoming invasive and frequently dominating the environments into which they have been introduced. Such species include

Water hyacinth ''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth is an aquatic plant native to South America, naturalized throughout the world, and often invasive outside its native range.New Zealand stonecrop is a highly invasive plant in temperate climates spreading from a marginal plant to encompassing the whole body of many ponds to the almost total exclusion of other plants and wildlife Other notable invasive plant species include floating pennywort, Curly leaved pondweed, the fern ally

Water fern Water fern is a common name for several plants and may refer to: * Salviniales, an order of aquatic ferns * '' Austroblechnum lanceolatum'', syn. ''Blechnum chambersii'', lance water fern * '' Austroblechnum patersonii'', syn. ''Blechnum patersonii' ...

and Parrot's feather. Many of these invasive plants have been sold as oxygenating plants for aquaria or decorative plants for garden ponds and have then been disposed of into the environment. In 2012, a comprehensive overview of alien aquatic plants in 46 European countries found 96 alien aquatic species. The aliens were primarily native to North America, Asia, and South America. The most spread alien plant in Europe was '' Elodea canadensis'' (Found in 41 European countries) followed by ''Azolla filiculoides'' in 25 countries and ''

Vallisneria spiralis ''Vallisneria spiralis'', also known as straight vallisneria, tape grass, or eel grass is a common aquarium plant that prefers good light and a nutrient rich substrate. In the wild, it can be found in tropical and sub-tropical regions worldwide ...

'' in 22 countries. The countries with the most recorded alien aquatic plant species were France and Italy with 30 species followed by Germany with 27 species, and Belgium and Hungary with 26 species. The European and Mediterranean Plant Protection Organization has published recommendations to European nations advocating the restriction or banning of the trade in invasive alien plants.

References

External links

* https://web.archive.org/web/20200410235322/https://aquaplant.tamu.edu/ * http://aswm.org * http://plants.ifas.ufl.edu
Aquatic Plant Monitoring in the State of Washington
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Distribution

Evolution

Aquatic adaptation

Reproduction

Photosynthesis

Morphology

Buoyancy

Terrestrial plants in aquatic environments

Classification of macrophytes

Emergent

Submerged

Floating-leaved

Free-floating

Morphological classification

Functions of macrophytes in aquatic systems

Uses and importance to humans

Food crops

Bioassessment

Potential sources of therapeutic agents

Wastewater treatment

Invasive aquatic plants

See also

References

External links