Aquatic plant

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The flower of Nymphaea alba, a species of water lily Nymphaea alba.jpg
The flower of Nymphaea alba , a species of water lily
Bud of Nelumbo nucifera, an aquatic plant. Nelumbo nucifera LOTUS bud.jpg
Bud of Nelumbo nucifera , an aquatic plant.

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 grows in or near water and is either emergent, submergent, or floating. In lakes and rivers macrophytes provide cover for fish , substrate for aquatic invertebrates, produce oxygen, and act as food for some fish and wildlife. [1]

Contents

Macrophytes are primary producers and are the basis of the food web for many organisms. [2] They have a significant effect on soil chemistry and light levels [3] 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. [4] [5] Seaweeds are multicellular marine algae and, although their ecological impact is similar to other larger water plants, they are not typically referred to as macrophytes [5] .

Aquatic plants require special adaptations for living submerged in water, or at the water's surface. The most common adaptation is the presence of lightweight internal packing cells, aerenchyma, but floating leaves and finely dissected leaves are also common. [6] [7] [8] Aquatic plants can only grow in water or in soil that is frequently saturated with water. They are therefore a common component of wetlands. [9] One of the largest aquatic plants in the world is the Amazon water lily; one of the smallest is the minute duckweed. Many small aquatic animals use plants such as duckweed for a home, or for protection from predators. Some other familiar examples of aquatic plants might include floating heart, water lily, lotus, and water hyacinth.

Distribution

The principal factor controlling the distribution of aquatic plants is the depth and duration of flooding. However, other factors may also control their distribution, abundance, and growth form, including nutrients, disturbance from waves, grazing, and salinity. [9] A few aquatic plants are able to survive in brackish, saline, and salt water. [6]

Evolution

Aquatic plants have adapted to live in either freshwater or saltwater. Aquatic vascular plants have originated on multiple occasions in different plant families; [6] [10] they can be ferns or angiosperms (including both monocots and dicots). The only angiosperms capable of growing completely submerged in seawater are the seagrasses. [11] Examples are found in genera such as Thalassia and Zostera . 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. [12] Archefructus represents one of the oldest, most complete angiosperm fossils which is around 125 million years old. [13] These plants require special adaptations for living submerged in water or floating at the surface. [13]

Although most aquatic plants can reproduce by flowering and setting seeds, many have also evolved to have extensive asexual reproduction by means of rhizomes, turions, and fragments in general. [7]

Classification of Macrophytes

Based on growth form, macrophytes can be charecterised as:

Emergent

An emergent plant is one which grows in water but pierces the surface so that it is partially in air. Collectively, such plants are emergent vegetation.

This habit may have developed because the leaves can photosynthesis 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 insects. [15]

There are many species of emergent plants, among them, the reed ( Phragmites ), Cyperus papyrus , Typha species, flowering rush and wild rice species. Some species, such as purple loosestrife, may grow in water as emergent plants but they are capable of flourishing in fens or simply in damp ground. [16]

Submerged

Submerged macrophytes completely grow under water with roots attached to the substrate (e.g. Myriophyllum spicatum ) or without any root system (e.g. Ceratophyllum demersum ). Helophytes are plants that grows in a marsh, partly submerged in water, so that it regrows from buds below the water surface [17] . Fringing stands of tall vegetation by water basins and rivers may include helophytes. Examples include stands of Equisetum fluviatile , Glyceria maxima , Hippuris vulgaris , Sagittaria , Carex , Schoenoplectus , Sparganium , Acorus , yellow flag ( Iris pseudacorus ), Typha and Phragmites australis . [17]

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), pondweeds (family Potamogetonaceae). [18]

Free-floating

Free-floating macrophytes are aquatic plants that are found suspended on water surface with their root not attached to 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. [18]

Morphological classification

Water lilies grow rooted in the bottom with leaves that float on the water surface. FloatingRedBlueLilies.JPG
Water lilies grow rooted in the bottom with leaves that float on the water surface.

The many possible classifications of aquatic plants are based upon morphology. [6] One example has six groups as follows: [19]

Marchantiales cf Conocephalum 20071111.jpg
Many liverworts grow either submerged or on land.
CeratophyllumSubmersum.jpg
Ceratophyllum submersum , a free-floating plant that grows completely submerged
Waterlettuce.jpg
Pistia stratiotes , an example of a pleuston, a plant that floats freely on the water surface
Lysichton americanus in Lochnabo Burn, Scotland.jpg
Lysichiton americanus grows rooted in the bottom with leaves and flowers above the waterline.

Functions of macrophytes in aquatic system

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 dissolve nutrients (N and P) from water. [3] Macrophytes are widely used in constructed wetlands around the world to remove excess N and P from polluted water. [20] 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. [21] Macrophytes promote the sedimentation of suspended solids by reducing the current velocities, [22] impede erosion by stabilising soil surfaces. [23] Macrophytes also provide spatial heterogeneity in otherwise unstructured water column. Habitat complexity provided by macrophytes like to increase the richness of taxonomy and density of both fish and invertebrates. [24]

Uses and importance to humans

Food crops

World aquaculture production of food fish and aquatic plants, 1990-2016 World aquaculture production of food fish and aquatic plants, 1990-2016.svg
World aquaculture production of food fish and aquatic plants, 1990–2016

Some aquatic plants are used by humans as a food source. Examples include wild rice ( Zizania ), water caltrop ( Trapa natans ), Chinese water chestnut ( Eleocharis dulcis ), Indian lotus ( Nelumbo nucifera ), water spinach ( Ipomoea aquatica ), and watercress ( Rorippa nasturtium-aquaticum ).

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, herbicides, or saliniation. Conversely, overly high nutrient levels may create an overabundance of macrophytes, which may in turn interfere with lake processing. [1] Macrophyte levels are easy to sample, do not require laboratory analysis, and are easily used for calculating simple abundance metrics. [1]

Potential sources of therapeutic agents

Phytochemical and pharmacological researches suggest that freshwater macrophytes, such as Centella asiatica , Nelumbo nucifera , Nasturtium officinale , Ipomoea aquatica and Ludwigia adscendens , are promising sources of anticancer and antioxidative natural products. [25]

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 inhibitory activity. Hot water extract prepared from the leaf of Ludwigia adscendens exhibits alpha-glucosidase inhibitory activity more potent than that of acarbose. [26]

See also

Related Research Articles

Alismatales order of plants

The Alismatales (alismatids) are an order of flowering plants including about 4500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats.

Nymphaeaceae Family of plants

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 five genera with about 70 known species. Water lilies are rooted in soil in bodies of water, with leaves and flowers floating on or emergent from the surface. The leaves are round, with a radial notch in Nymphaea and Nuphar, but fully circular in Victoria and Euryale.

Wetland A land area that is permanently or seasonally saturated with water

A wetland is a distinct ecosystem that is flooded by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, and support of plants and animals. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, and the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it. Methods for rapidly assessing these functions, wetland ecological health, and general wetland condition have been developed in many regions and have contributed to wetland conservation partly by raising public awareness of the functions and the ecosystem services some wetlands provide.

Salt marsh A coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides

A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated by dense stands of salt-tolerant plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh in trapping and binding sediments. Salt marshes play a large role in the aquatic food web and the delivery of nutrients to coastal waters. They also support terrestrial animals and provide coastal protection.

Constructed wetland An artificial wetland to treat municipal or industrial wastewater, greywater or stormwater runoff

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

Aquatic ecosystem An ecosystem in a body of water

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

Hydrosere A type of Plant Succession

A hydrosere is a plant succession which occurs in an area of fresh water such as in oxbow lakes and kettle lakes. In time, an area of open freshwater will naturally dry out, ultimately becoming woodland. During this change, a range of different landtypes such as swamp and marsh will succeed each other.

<i>Luronium</i> species of plant

Luronium natans is a species of aquatic plant commonly known as the floating water-plantain. It is the only recognized species in the genus Luronium, native to western and central Europe, from Spain to Britain to Norway east to Ukraine.

River ecosystem type of aquatic ecosystem with flowing freshwater

River ecosystems are flowing waters that drain the landscape, and include the biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions of its many parts. River ecosystems are part of larger watershed networks or catchments, where smaller headwater streams drain into mid-size streams, which progressively drain into larger river networks.

A lake ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions.

<i>Egeria densa</i> species of plant

Egeria densa, the large-flowered waterweed or Brazilian waterweed, is a species of Egeria native to warm temperate South America in southeastern Brazil, Argentina, and Uruguay. It is considered a problematic invasive species due to its use in home aquariums and subsequent release into non-native habitats.

<i>Nymphoides peltata</i> species of plant

Nymphoides peltata is perennial, rooted aquatic plant with floating leaves of the family Menyanthaceae.

<i>Utricularia inflata</i> species of plant

Utricularia inflata, commonly known as the swollen bladderwort, inflated bladderwort, or large floating bladderwort, is a large suspended aquatic carnivorous plant that belongs to the genus Utricularia. It is a perennial that is native to the southeastern coastal plains of the United States. It has often been confused with U. radiata, which is similar but smaller than U. inflata. Since 1980, U. inflata has been reported to exist in locations beyond its traditional range, such as the Adirondack Mountains in New York, southeastern Massachusetts, and in Washington State. Studies on the populations in the Adirondacks suggest that an introduction of U. inflata to a location where it naturalizes can lead to altered sediment chemistry by reducing the net primary productivity of native species. It is also listed by the state of Washington as a problematic species because of the dense mat-forming habit of this aquatic Utricularia. It is one of the few carnivorous plants that can be invasive.

<i>Potamogeton perfoliatus</i> species of plant

Potamogeton perfoliatus is a perennial aquatic plant in the family Potamogetonaceae occurring in both standing and flowing freshwater habitats. It is widely distributed globally, occurring in all continents except South America and Antarctica.

Freshwater marsh type of marsh

A freshwater marsh is a non-tidal, non-forested marsh wetland that contains fresh water, and is continuously or frequently flooded. Freshwater marshes primarily consist of sedges, grasses, and emergent plants. Freshwater marshes are usually found near the mouths of rivers, along lakes, and are present in areas with low drainage like abandoned oxbow lakes. It is the counterpart to the salt marsh, an upper coastal intertidal zone of bio-habitat, which is regularly flushed with sea water.

<i>Potamogeton lucens</i> species of plant

Potamogeton lucens, or shining pondweed, is an aquatic perennial plant native to Eurasia and North Africa. It grows in relatively deep, still or slow-flowing, calcareous freshwater habitats.

<i>Panicum hemitomon</i> species of plant

Panicum hemitomon is a species of grass known by the common name maidencane. It is native to North America, where it occurs along the southeastern coastline from New Jersey to Texas. It is also present in South America.

<i>Ludwigia adscendens</i> species of plant

Ludwigia adscendens, the water primrose, is a species of flowering plant in the evening primrose family. Its native distribution is unclear. It is now a common weed of rice paddies in Asia and occurs also in Australia and Africa, but may have originated in South America.

<i>Glossostigma cleistanthum</i> species of plant

Glossostigma cleistanthum, also known as mudmat, is a freshwater aquatic plant native to Australia, New Zealand, India and East Africa. It is a cleistogamous plant, which is a type of self-pollinating plant that can propagate using non-opening flowers. Where growth is submerged, the leaves are between 0.5–2.5 inches long and bear closed, self-pollinating flowers. These leaves are nearly sessile and grow along the stem in alternating pairs that resemble rabbit ears. Where water recedes and growth is emergent, the leaves are much smaller, ranging between 0.2–0.5 inches in length. The emergent plants produce insect-pollinated flowers located on short stalks. It belongs to the family Phrymaceae which includes annuals and perennials.

<i>Podostemum ceratophyllum</i> species of plant

Podostemum ceratophyllum, commonly known as the hornleaf riverweed, is a species of submerged aquatic plant in the family Podostemaceae. It is native to eastern North America where it grows on hard bottoms in swiftly flowing rivers and streams and is considered a foundation species.

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