Pistia | |
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Monocots |
Order: | Alismatales |
Family: | Araceae |
Subfamily: | Aroideae |
Tribe: | Pistieae |
Genus: | Pistia L. [2] |
Species: | P. stratiotes |
Binomial name | |
Pistia stratiotes | |
Range of the genus Pistia | |
Synonyms [4] | |
List
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Pistia is a genus of aquatic plants in the arum family, Araceae. It is the sole genus in the tribe Pistieae which reflects its systematic isolation within the family. [5] The single species it comprises, Pistia stratiotes, is often called water cabbage, water lettuce, Nile cabbage, or shellflower. Its native distribution is uncertain but is probably pantropical; it was first scientifically described from plants found on the Nile near Lake Victoria in Africa. [6] It is now present, either naturally or through human introduction, in nearly all tropical and subtropical fresh waterways and is considered an invasive species as well as a mosquito breeding habitat. The specific epithet is derived from a Greek word, στρατιώτης, meaning "soldier", which references the sword-shaped leaves of some plants in the Stratiotes genus. [7]
Pistia stratiotes is a perennial monocotyledon with thick, soft leaves that form a rosette. [8] It floats on the surface of the water, its roots hanging submersed beneath floating leaves. The leaves can measure 2 – 15 cm long and are light green, with parallel venations and wavy margins. [8] The surface of the leaves is covered in short, white hairs which form basket-like structures that can trap air bubbles and increase the plant's buoyancy. The spongy parenchyma with large intercellular spaces in the leaves also aids the plant in floating. [9] The flowers are dioecious, lack petals, and are hidden in the middle of the plant amongst the leaves. Pistia stratiotes has a spadix inflorescence, containing one pistillate flower with one ovary and 2–8 staminate flowers with two stamens. [10] The pistillate and carpellate flowers are separated by folds in the spathe, where the male flowers are located above the female flowers. [5] Oval, green berries with ovoid seeds form after successful fertilization. The plant undergoes asexual reproduction by propagating through stolons, yet evidence of sexual reproduction has also been observed in the ponds of Southern Brazil. [11]
Pistia stratiotes are found in slow-moving rivers, lakes, and ponds. The species displays optimal growth in the temperature range of 22–30 °C, but can endure extreme temperatures up to 35 °C. [12] As a result, Pistiastratiotes do not grow in colder temperatures, beyond the tropics of Cancer and Capricorn. The species also require slightly acidic water in the pH range of 6.5–7.2 for optimal growth. [12]
Water lettuce is among the world's most productive freshwater aquatic plants and is considered an invasive species. [13] The species can be introduced to new areas by water dispersal, fragmentation, and hitchhiking on marine transportation or fishing equipment. [14] The invasion of Pistia stratiotes in the ecosystem can lead to environmental and socio-economic ramifications to the community it serves. In waters with high nutrient content, particularly those that have been contaminated with human loading of sewage or fertilizers, water lettuce can exhibit weedy overgrowth. It may also become invasive in hydrologically altered systems such as flood control canals and reservoirs. [15] The severe overgrowth of water lettuce can block gas exchange in the surface water, creating hypoxic conditions and eliminating or disrupting various native marine organisms. [16] Blocking access to sunlight, large mats of water lettuce can shade native submerged plants and alter communities relying on these native plants as a source of food. [17] The growth of these mats can also get tangled in boat propellers and create challenges for boaters or recreational fishermen. [18]
Pistia stratiotes feature in the life cycles of certain insect vectors for malaria and filariasis. [19] Mosquitoes of the genus Mansonia can lay their eggs under the leaves of aquatic plants, such as Pistia stratiotes. Twenty-four hours later, the emerging larvae attach to the plant's roots using its siphon tube for respiration. Within a week, larvae can develop into adult mosquitos, making Pistia stratiotes a potential breeding ground for vectors of infectious disease. [20] The moth Samea multiplicalis also uses Pistia stratiotes as its primary host plant. Eggs are laid among leaves and stems of the host plant and larvae hatch and feed intensively as they develop. [21]
The species is set to be banned in the EU from August of 2024 to prevent spreading. [28]
The center of origin of Pistia stratiotes has long been a source of debate. [29] Nativity to northern Africa is indicated by Egyptian hieroglyphics and reports of plants meeting the description of Pistia by Greek botanists, Dioscorides and Theophrastus in the Nile River. [6] In addition, the co-evolution of Pistia stratiotes with various insects native to Brazil and Argentina, such as the water lettuce weevil, [30] indicates a long-term native tenure in South America. [31] Fossil specimens dating back to the late Pleistocene (~12,000 BP) and early Holocene (~3,500 BP) period are reported from Florida, indicating a native presence in the southeastern United States. [32] Recent genetic evidence also suggests that Pistia is not actually a monotypic genus, as had been long assumed. [33] Instead, Pistia appears to be composed of at least three genetically distinct, but morphologically and ecologically similar, species at a global scale. [33]
Though Pistia stratiotes is intolerant of cold temperatures, it has been recorded growing at least temporarily in temperate areas of North America and Europe. [4] [34] In the United States north of the Gulf of Mexico it has been found growing in Colorado, Connecticut, Delaware, Illinois, Kansas, Maryland, Michigan, Minnesota, Missouri, New York, North Carolina, Ohio, Rhode Island, South Carolina, and Wisconsin. One of these occurrences, in Idaho, survives in an area of a river fed by a hot spring. The rest are thought either to be completely eradicated by cold weather or possibly to survive by seed production. [35]
Pistia-like plants appear in the fossil record during the Late Cretaceous epoch in rock strata from the western interior of North America. They were first described as †Pistia corrugata by Leo Lesquereux in 1876 based on specimens from the Almond Formation of Wyoming (late Campanian age). However, based on more complete specimens from the Campanian Dinosaur Park Formation of southern Alberta, Canada, and other areas, they were redescribed as a separate genus, †Cobbania, primarily due to differences in leaf morphology. [36] [37] Younger fossils attributed to Pistiastratiotes have described from Eocene strata in the southeastern United States, [38] and 350 fossil seeds of †Pistia sibirica have been described from middle Miocene strata of the Fasterholt area near Silkeborg in Central Jutland, Denmark. Fossils of this species have also been described from the Oligocene and Miocene of Western Siberia and from the Miocene of Germany. [39]
A specimen of Pistia from the Florida peninsula dating from at least 3,550 years Before Present and a report of Holocene Pistia fossils from a lake in south central Florida are consistent with genetic evidence indicating that some varieties of Pistia stratiotes are native to the southeastern United States. [33] [38] [40]
While considered edible, Pistia stratiotes is not palatable as it is rich in calcium oxalate crystals that are bitter in taste. Nevertheless, there are records of the plant being utilized as famine food in India during the Great Famine of 1876–1878. [41]
The Hausa people of Nigeria used the ash of the plant as a substitute for salt due to its high concentration of potassium chloride, a mineral salt. [19] This salt substitute, also called zakankau, was of high importance, especially when imported salt was unavailable. [42]
Caution is advised when consuming Pistia stratiotes, as the plant is a hyperaccumulator, and can absorb and accumulate toxic heavy metals present in its environment. [43] The presence of high concentrations of calcium oxalate crystals can induce various health concerns, such as inhibited mineral absorption and kidney stones. [44] [45]
In Singapore and Southern China, Pistia stratiotes is commonly grown or collected as animal feed for ducks and pigs. [46] Water lettuce is also considered an alternative for poultry feed in Indonesia due to its high content of crude protein. [47]
There are various medical uses of Pistia stratiotes throughout regions in Asia and Africa. In Nigeria, the dried leaves are prepared into a powder form and are applied to wounds and sores for disinfection. [48] A similar use is present in Indian traditional medicine, where the powdered leaf is applied to syphilitic eruptions and skin infections. [49] In Nigeria and Gambia, the leaf is infused in water to create an eyewash to treat allergic conjunctivitis. [50] The eyewash is known to have a cooling and analgesic effect. Therefore, the plant is commonly called 'eye-pity' in Africa. [51] In addition, the leaves of Pistia stratiotes can be burned into ash, and in Indian and Nigerian traditional medicine, the ash is used in treating ringworm infections of the scalp. [49]
The high sorption property of water lettuce makes it a great candidate for biodegradable oil sorbents in marine oil spills. Particularly, the leaves of Pistiastratiotes can efficiently absorb significant amounts of hydrocarbons due to its large surface area and hydrophobicity. [55]
As a hyper-accumulator, Pistiastratiotes has been studied as a potential candidate for wastewater treatment plants. The roots and leaves of the plant have been found to absorb excess nutrients and heavy metals, such as zinc, chromium, and cadmium in contaminated waters. [56]
Pistiastratiotes can be grown in water gardens to reduce harmful algal blooms and eutrophic conditions. [57] The plant is able to control the growth of algae by restricting light penetration in the water column and competing for nutrients, with significant uptake of phosphorus and ammonia nitrogen. [58]
An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native species that become harmful to their native environment after human alterations to its food web. Since the 20th century, invasive species have become serious economic, social, and environmental threats worldwide.
Salvinia molesta, commonly known as giant salvinia, or as kariba weed after it infested a large portion of Lake Kariba between Zimbabwe and Zambia, is an aquatic fern, native to south-eastern Brazil. It is a free-floating plant that does not attach to the soil, but instead remains buoyant on the surface of a body of water. The fronds are 0.5–4 cm long and broad, with a bristly surface caused by the hair-like strands that join at the end to form eggbeater shapes. They are used to provide a waterproof covering. These fronds are produced in pairs also with a third modified root-like frond that hangs in the water. It has been accidentally introduced or escaped to countless lakes throughout the United States, including Caddo Lake in Texas, where the invasive species has done extensive damage, killing off other life.
Aquatic plants are vascular plants that have adapted to live in aquatic environments. They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes (phytoplanktons). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquatic animals such as fish, amphibians and aquatic insects, create substrate for benthic invertebrates, produce oxygen via photosynthesis, and serve as food for some herbivorous wildlife. Familiar examples of aquatic plants include waterlily, lotus, duckweeds, mosquito fern, floating heart, water milfoils, mare's tail, water lettuce and water hyacinth.
Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs.
Lythrum salicaria or purple loosestrife 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 Primulaceae. Other names include spiked loosestrife and purple Lythrum. This herbaceous perennial is native to Europe and Asia, and possibly Australia.
Phragmites is a genus of four species of large perennial reed grasses found in wetlands throughout temperate and tropical regions of the world.
Azolla is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, looking nothing like other typical ferns but more resembling the form of some mosses or even duckweeds. Azolla filiculoides is one of just two fern species for which a reference genome has been published. It is believed that this genus grew so prolifically during the Eocene that it triggered a global cooling event that has lasted to the present.
Centaurea diffusa, also known as diffuse knapweed, white knapweed or tumble knapweed, is a member of the genus Centaurea in the family Asteraceae. This species is common throughout western North America but is not actually native to the North American continent, but to the eastern Mediterranean.
Cirsium arvense is a perennial species of flowering plant in the family Asteraceae, native throughout Europe and western Asia, northern Africa and widely introduced elsewhere. The standard English name in its native area is creeping thistle. It is also commonly known as Canada thistle and field thistle.
Myriophyllum spicatum is a submerged aquatic plant which grows in still or slow-moving water. It 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 is considered to be a highly invasive species.
Pontederia 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. It is the sole species of the subgenus Oshunae within the genus Pontederia. Anecdotally, it is known as the "terror of Bengal" due to its invasive growth tendencies.
Lonicera maackii, the Amur honeysuckle, is a species of honeysuckle in the family Caprifoliaceae that is native to temperate eastern Asia; specifically in northern and western China south to Yunnan, Mongolia, Primorsky Krai in southeastern Siberia, Korea, and, albeit rare there, central and northern Honshū, Japan.
Lantana camara is a species of flowering plant in the verbena family (Verbenaceae), native to the American tropics. It is a very adaptable species, which can inhabit a wide variety of ecosystems; once it has been introduced into a habitat it spreads rapidly; between 45ºN and 45ºS and less than 1,400 metres in altitude.
There are a number of environmental issues in Florida. A large portion of Florida is a biologically diverse ecosystem, with large wetlands in the Everglades. Management of environmental issues related to the everglades and the larger coastal waters and wetlands have been important to the history of Florida and the development of multiple parts of the economy of Florida, including the influential agricultural industry. This biodiversity leaves much of Florida's ecological ecosystem vulnerable to invasive species and human sources of industrial pollution and waste.
Azolla pinnata is a species of fern known by several common names, including mosquitofern, feathered mosquitofern and water velvet. It is native to much of Africa, Asia and parts of Australia. It is an aquatic plant, it is found floating upon the surface of the water. It grows in quiet and slow-moving water bodies because swift currents and waves break up the plant. At maximum growth rate, it can double its biomass in 1.9 days, with most strains attaining such growth within a week under optimal conditions.
Pontederia azurea is a water hyacinth from the Americas, sometimes known as anchored water hyacinth. It is the type species of Pontederia subg. Eichhornia, which was previously recognized as part of the polyphyletic genus Eichhornia. It is of some interest as an aquarium plant.
Samea multiplicalis, the salvinia stem-borer moth, is an aquatic moth commonly found in freshwater habitats from the southern United States to Argentina, as well as in Australia where it was introduced in 1981. Salvinia stem-borer moths lay their eggs on water plants like Azolla caroliniana, Pistia stratiotes, and Salvinia rotundifolia. Larval feeding on host plants causes plant death, which makes S. multiplicalis a good candidate for biological control of weedy water plants like Salvinia molesta, an invasive water fern in Australia. However, high rates of parasitism in the moth compromise its ability to effectively control water weeds. S. multiplicalis larvae are a pale yellow to green color, and adults develop tan coloration with darker patterning. The lifespan, from egg to the end of adulthood is typically three to four weeks. The species was first described by Achille Guenée in 1854.
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 from within the arum or aroid family (Araceae), so often are classified as the subfamily Lemnoideae within the family Araceae. Other classifications, particularly those created prior to the end of the twentieth century, place them as a separate family, Lemnaceae.
Centaurea stoebe, the spotted knapweed or panicled knapweed, is a species of Centaurea native to eastern Europe, although it has spread to North America, where it is considered an invasive species. It forms a tumbleweed, helping to increase the species' reach, and the seeds are also enabled by a feathery pappus.
Aquatic plant management involves the science and methodologies used to control invasive and non-invasive aquatic plant species in waterways. Methods used include spraying herbicide, biological controls, mechanical removal as well as habitat modification. Preventing the introduction of invasive species is ideal.
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