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42-460: Lemnaceae 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

84-548: A tropical rainforest and produces some of the most spectacular wildflowers in the world. It is however, severely threatened by climate change which has moved the winter rain belt south, and also by clearing for agriculture and through use of fertilizers , which is primarily driven by low land costs which make farming economic even with yields a fraction of those in Europe or North America. An example of oligotrophic soils are those on white-sands, with soil pH lower than 5.0, on

126-947: A botanical subfamily. Detarioideae is a subdivision of the family Fabaceae (legumes), containing 84 genera. Stevardiinae is an example of a zoological subfamily. Stevardiinae is a large subdivision of the family Characidae , a diverse clade of freshwater fish . This biology article is a stub . You can help Misplaced Pages by expanding it . Oligotrophic An oligotroph is an organism that can live in an environment that offers very low levels of nutrients . They may be contrasted with copiotrophs , which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates of metabolism, and generally low population density. Oligotrophic environments are those that offer little to sustain life. These environments include deep oceanic sediments, caves, glacial and polar ice, deep subsurface soil, aquifers, ocean waters, and leached soils. Examples of oligotrophic organisms are

168-476: A large abundance of psychrophiles that are well adapted to living in an Antarctic biome. Most oligotrophs live in lakes where water helps support biochemical processes for growth and survival. Below are some documented examples of oligotrophic environments in Antarctica: Lake Vostok , a freshwater lake which has been isolated from the world beneath 4 km (2.5 mi) of Antarctic ice

210-531: A role in conservation of water because a cover of duckweed will reduce evaporation of water when compared to the rate of a similarly sized water body with a clear surface. Duckweed also functions as a bioremediator by effectively filtering contaminants such as bacteria, nitrogen, phosphates, and other nutrients from naturally occurring bodies of water, constructed wetlands, and wastewater. A start-up, microTERRA, based in Mexico has attempted to use duckweed to clean

252-558: A taxonomic mystery, and usually have been considered to be their own family, the Lemnaceae. They primarily reproduce asexually. Flowers, if present at all, are small. Roots are either very much reduced, or absent entirely. They were suspected of being related to the Araceae as long ago as 1876, but until the advent of molecular phylogeny , testing this hypothesis was difficult. Starting in 1995, studies began to confirm their placement in

294-438: Is a good candidate as a biofuel because it grows rapidly, produces five to six times as much starch as corn per unit of area, and does not contribute to global warming . The rapid nature of duckweed has shown that it can double biomass within four and a half days. Duckweed removes carbon dioxide from the atmosphere, and it may have value for climate change mitigation . The plants can provide nitrate removal, if cropped, and

336-455: Is adapted to rapid growth and an aquatic lifestyle. Duckweed is being studied by researchers around the world as a possible source of clean energy. In the U.S., in addition to being the subject of study by the DOE, both Rutgers University and North Carolina State University have ongoing projects to determine whether duckweed might be a source of cost-effective, clean, renewable energy . Duckweed

378-572: Is also cultivated as a vegetable in Israel . It produces more protein per square meter than soybeans , so sometimes it is cited as a significant potential food source. Some initial investigations, into what extent duckweed could be introduced to European markets, show little consumer objection to the idea. NASA 's Caves of Mars Project identified duckweed as a top candidate for Martian food production projects. Despite some of these benefits, because duckweed thrives in high-nutrient wetland environments,

420-467: Is frequently held to be a primary example of an oligotrophic environment. Analysis of ice samples showed ecologically separated microenvironments. Isolation of microorganisms from each microenvironment led to the discovery of a wide range of different microorganisms present within the ice sheet. Traces of fungi have also been observed which suggests potential for unique symbiotic interactions. The lake’s extensive oligotrophy has led some to believe parts of

462-520: Is low, and remobilise them when demand increases. Oligotrophs occupy environments where the available nutrients offer little to sustain life. The term “ oligotrophic ” is commonly used to describe terrestrial and aquatic environments with very low concentrations of nitrates, iron, phosphates, and carbon sources. Oligotrophs have acquired survival mechanisms that involve the expression of genes during periods of low nutrient conditions, which has allowed them to find success in various environments. Despite

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504-419: Is mostly by asexual budding ( vegetative reproduction ), which occurs from a meristem enclosed at the base of the frond. Occasionally, three tiny "flowers" consisting of two stamens and a pistil are produced, by which sexual reproduction occurs. Some view this "flower" as a pseudanthium , or reduced inflorescence , with three flowers that are distinctly either female or male and which are derived from

546-443: Is reduced by very slow growth rates, and by efficient use of low-availability nutrients; for example, the use of highly available ions to maintain turgor pressure , with low-availability nutrients reserved for the building of tissues. Despite these adaptations, nutrient requirement typically exceed uptake during the growing season, so many oligotrophic plants have the ability to store nutrients, for example, in trunk tissues, when demand

588-476: Is the presence of fungi, because Collimonas have the ability of not only hydrolyzing the chitin produced by fungi for nutrients, but also producing materials (e.g., P. fluorescens 2-79) to protect themselves from fungal infection. The mutual relationship is common in the oligotrophic environments. Additionally, Collimonas can also obtain electron sources from rocks and minerals by weathering . In terms of polar areas, such as Antarctic and Arctic region,

630-518: The Cambrian and there has been no glaciation to renew soils since the Carboniferous . Thus, soils are extremely nutrient-poor and most vegetation must use strategies such as cluster roots to gain even the smallest quantities of such nutrients as phosphorus and sulfur . The vegetation in these regions, however, is remarkable for its biodiversity , which in places is as great as that of

672-824: The Miocene of the Czech Republic . Unusually complete specimens from the Paleocene of Alberta , Canada, range from single leaves up to about 4 cm (1.6 in) in diameter to rosettes of up to four leaves, some of which were connected to adjacent plants by stolons , and a few of which bear remains of flowers with anthers that contain Pandaniidites pollen. Occurrences of lemnoid seeds described as Lemnospermum have also been reported. Research and applications of duckweeds are promoted by two international organizations, The International Lemna Association and

714-582: The Rio Negro basin on northern Amazonia that house very low-diversity, extremely fragile forests and savannahs drained by blackwater rivers ; dark water colour due to high concentration of tannins , humic acids and other organic compounds derived from the very slow decomposition of plant matter. Similar forests are found in the oligotrophic waters of the Patía River delta on the Pacific side of

756-442: The spadix in the Araceae. Evolution of the duckweed inflorescence remains ambiguous due to the considerable evolutionary reduction of these plants from their earlier relatives. The flower of the duckweed genus Wolffia is the smallest known, measuring merely 0.3 mm long. The fruit produced through this occasional reproduction is a utricle , and a seed is produced in a bag containing air that facilitates flotation. One of

798-639: The Andes. In the ocean , the subtropical gyres north and south of the equator are regions in which the nutrients required for phytoplankton growth (for instance, nitrate , phosphate and silicic acid ) are strongly depleted all year round. These areas are described as oligotrophic and exhibit low surface chlorophyll . They are occasionally described as "ocean deserts". The oligotrophic soil environments include agricultural soil, frozen soil, et cetera . Various factors, such as decomposition , soil structure, fertilization and temperature , can affect

840-455: The Araceae and since then, most systematists consider them to be part of that family. Their position within their family has been slightly less clear; however, several twenty-first century studies place them in the position shown below. Although they are in the same family as Pistia , another aquatic plant, they are not closely related. Gymnostachydoideae Orontioideae (skunk cabbages and golden club) Lemnoideae (duckweeds) most of

882-724: The International Steering Committee on Duckweed Research and Applications. In July 2008, the U.S. Department of Energy (DOE) Joint Genome Institute announced that the Community Sequencing Program would fund sequencing of the genome of the giant duckweed, Spirodela polyrhiza . This was a priority project for DOE in 2009. The research was intended to facilitate new biomass and bioenergy programs. The results were published in February 2014. They provide insight into how this plant

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924-607: The capability to live in low nutrient concentrations, oligotrophs may find difficulty surviving in nutrient-rich environments. The presence of excess nutrients overwhelm oligotroph's metabolic systems, which cause them to struggle to regulate nutrient uptake. For example, oligotroph's enzymes function well in low nutrient environments, but struggle in high nutrient environments. Antarctic environments offer very little to sustain life as most organisms are not well adapted to live under nutrient-limiting conditions and cold temperatures (lower than 5 °C). As such, these environments display

966-781: The cave-dwelling olm ; the bacterium " Candidatus Pelagibacter communis ", which is the most abundant organism in the ocean (with an estimated 2 × 10 individuals in total); and lichens , with their extremely low metabolic rate . Etymologically , the word "oligotroph" is a combination of the Greek adjective oligos (ὀλίγος) meaning "few" and the adjective trophikos (τροφικός) meaning "feeding". Plant adaptations to oligotrophic soils provide for greater and more efficient nutrient uptake, reduced nutrient consumption, and efficient nutrient storage. Improvements in nutrient uptake are facilitated by root adaptations such as nitrogen-fixing root nodules , mycorrhizae and cluster roots . Consumption

1008-570: The duckweeds are important in the process of bioremediation because they grow rapidly, absorbing excess mineral nutrients, particularly nitrogen and phosphates . For these reasons, they are touted as water purifiers of untapped value. The Swiss Department of Water and Sanitation in Developing Countries, associated with the Swiss Federal Institute for Environmental Science and Technology, asserts that as well as

1050-476: The end of the twentieth century, place them as a separate family, Lemnaceae . These plants have a simple structure, lacking an obvious stem or leaves . The greater part of each plant is a small organized " thallus " or " frond " structure only a few cells thick, often with air pockets ( aerenchyma ) that allow it to float on or just under the water surface. Depending on the species, each plant may have no root or may have one or more simple rootlets. Reproduction

1092-437: The food and agricultural values, duckweed also may be used for wastewater treatment to capture toxins and for odor control, and that if a mat of duckweed is maintained during harvesting for removal of the toxins captured thereby, it prevents the development of algae and controls the breeding of mosquitoes . The same publication provides an extensive list of references for many duckweed-related topics. These plants also may play

1134-527: The lake are completely sterile. This lake is a helpful tool for simulating studies regarding extraterrestrial life on frozen planets and other celestial bodies. Crooked Lake is an ultra-oligotrophic glacial lake with a thin distribution of heterotrophic and autotrophic microorganisms. The microbial loop plays a big role in cycling nutrients and energy within this lake, despite particularly low bacterial abundance and productivity in these environments. The little ecological diversity can be attributed to

1176-536: The lake's low annual temperatures. Species discovered in this lake include Ochromonas , Chlamydomonas , Scourfeldia , Cryptomonas , Akistrodesmus falcatus , and Daphniopsis studeri (a microcrustacean). It is proposed that low competitive selection against Daphniopsis studeri has allowed the species to survive long enough to reproduce in nutrient limiting environments. The sandplains and lateritic soils of southern Western Australia , where an extremely thick craton has precluded any geological activity since

1218-416: The largest genome size (1,500 MB). DNA sequencing has shown that Wolffiella and Wolffia are more closely related than the others. Spirodela is at the basal position of the taxon, followed by Lemna , Wolffiella , and Wolffia , which is the most derived. Spirodela Lemna Wolffiella Wolffia To identify different duckweed genomes, a DNA-based molecular identification system

1260-464: The lemnoid pollen genus Pandaniidites . Fossils of floating leaves with rootlets from the Paleocene of southern Saskatchewan , Canada , that were originally described as Lemna ( Spirodela ) scutata by John William Dawson in 1885, have been redescribed as Limnobiophyllum . In addition to western North America, Limnobiophyllum has been reported from the Paleocene of eastern Russia and

1302-499: The more important factors influencing the distribution of wetland plants, and aquatic plants in particular, is nutrient availability. Duckweeds tend to be associated with fertile, even eutrophic conditions. They can be spread by sticking to the feathers of waterfowl and the skin or fur of other amphibious animals, and thus transported inadvertently to new bodies of water. The plants may also be transported by flooding or other moving water. In water bodies with constant currents or overflow,

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1344-406: The nutrient-availability in the soil environments. Generally, the nutrient becomes less available along the depth of the soil environment, because on the surface, the organic compounds decomposed from the plant and animal debris are consumed quickly by other microbes, resulting in the lack of nutrient in the deeper level of soil. In addition, the metabolic waste produced by the microorganisms on

1386-458: The plants are carried down the channels and do not typically proliferate greatly, as they prefer still waters. However, in some locations, a cyclical pattern exists, driven by weather patterns, in which the plants proliferate greatly during periods of low water movement before they are carried away as rainy periods ensue. Duckweed is an important, high- protein food source for waterfowl and many species of fish . The tiny plants provide cover for

1428-544: The plants can be seen as a nuisance species when conditions favor excessive proliferation in environments that are traditionally low in nutrients or oligotrophic . One example of this problem occurs within the Everglades , a mostly oligotrophic environment, when excess chemicals (that include fertilizers) are carried by storm runoff, or surface runoff , into its waterways. Urban runoff and agricultural pollution then begin to introduce increased levels of nutrients into

1470-440: The rest of the family Araceae The genera of duckweeds are: Spirodela , Landoltia , Lemna , Wolffiella , and Wolffia . Duckweed genome sizes have a ten-fold range (150~1,500 MB), potentially representing diploids to octaploids . The ancestral genus of Spirodela has the smallest genome size (150 MB, similar to Arabidopsis thaliana ), while the most derived genus, Wolffia , contains plants with

1512-403: The soil environment is considered as oligotrophic because the soil is frozen with low biological activities. The most abundant species in the frozen soil are Actinomycetota , Pseudomonadota , Acidobacteriota and Cyanobacteria , together with a small amount of archaea and fungi. Actinomycetota can maintain the activity of their metabolic enzymes and continue their biochemical reactions under

1554-430: The soil provides the alternative sources for the species living in the oligotrophic soil. In terms of the agricultural lands, the application of fertilizer has a complicated impact on the source of carbon, either increasing or decreasing the organic carbon in the soil. Collimonas is one of the genera that are capable of living in the oligotrophic soil. One common feature of the environments where Collimonas lives

1596-410: The surface also causes the accumulation of toxic chemicals in the deeper area. Furthermore, oxygen and water are important for some metabolic pathways, but it is difficult for water and oxygen to diffuse as the depth increases. Some factors such as: soil aggregates, pores and extracellular enzymes, may help water, oxygen and other nutrients diffuse into the soil. Moreover, the presence of mineral under

1638-470: The surrounding wetlands and waterways, which can cause a disruption to native ecology. These conditions allow for the invasion of a fast growing species such as duckweed to establish themselves, spread, and displace other native species such as sawgrass , and over time, result in widespread changes to the ecology of native sawgrass and slough habitats within the Everglades. The duckweeds have long been

1680-436: The vulnerable fry and tadpoles of many fishes and amphibians . The plants are used as shelter by pond species, such as bullfrogs and newts , and fish such as bluegills . They also provide shade and, although frequently confused with them, can reduce certain light-generated growths of photoautotrophic algae . Duckweed is consumed in some parts of Southeast Asia, namely Laos , Thailand , and Myanmar . In addition, it

1722-415: The water in privately owned aquaculture farms. The plants use nitrogen and phosphorus produced from fish waste as fertilizer, while simultaneously cleaning the water as it grows. The water can then be reused by the aquaculture farmers, and the duckweed, which has a 35-42% protein content, can be harvested as a source of sustainable plant-based protein . Subfamily Detarioideae is an example of

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1764-746: Was developed based on seven plastid -markers proposed by the Consortium for the Barcode of Life . The atpF-atpH non-coding spacer was chosen as a universal DNA barcoding marker for species-level identification of duckweeds. Extinct free-floating aquatic plants and pollen with affinities to the Lemnoideae first appear in the fossil record during the Late Cretaceous ( Maastrichtian ) as evidenced by floating leaves described as Aquaephyllum auriculatum from Patagonia , Argentina , and

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