Wild rice are four species of grasses forming the genus Zizania, and the grain that can be harvested from them. The grain was historically gathered and eaten in both North America and China, while now a delicacy in North America, the grain is eaten less in China, where the plants stem is used as a vegetable. Wild rice is not directly related to Asian rice, whose wild progenitors are O. rufipogon and O. nivara, although they are close cousins, wild-rice grains have a chewy outer sheath with a tender inner grain that has a slightly vegetal taste. The plants grow in water in small lakes and slow-flowing streams, often. The grain is eaten by dabbling ducks and other aquatic wildlife, wild rice, an annual, grows in the Saint Lawrence River and on the Atlantic and Gulf coasts of the United States. Texas wild rice is a plant found only in a small area along the San Marcos River in central Texas. One species is native to Asia, Manchurian wild rice, is a native to China. Texas wild rice is in danger of extinction due to loss of habitat in its limited range.
The pollen of Texas wild rice can only travel about 30 inches away from a parent plant, if pollen does not land on a receptive female flower within that distance, no seeds are produced. Manchurian wild rice has almost disappeared from the wild in its native range, the species most commonly harvested as grain are annual species, Zizania palustris is now grown commercially, but Zizania aquatica was used extensively in the past by Indians. Native Americans and others harvest wild rice by canoeing into a stand of plants, the size of the knockers, as well as other details, are prescribed in state and tribal law. By Minnesota statute, knockers must be at most 1 in diameter,30 in long, the plants are not beaten with the knockers but require only a gentle brushing to dislodge the mature grain. The Ojibwa people call this plant manoomin, meaning harvesting berry, some seeds fall to the muddy bottom and germinate in the year. Several Native American cultures, such as the Ojibwa, consider wild rice to be a component in their culture.
Tribes that are recorded as historically harvesting Zizania aquatica are the Dakota, Meskwaki, Omaha, Thompson, Native people who utilized Zizania palustris are the Chippewa and Potawatomi. The rice is harvested with a canoe, one person vans rice into the canoe with two small poles while the other paddles slowly or uses a push pole, for these groups, this harvest is an important cultural event. The Menominee tribe were named Omanoominii by the neighboring Ojibwa after this plant, because of its nutritional value and taste, wild rice increased in popularity in the late 20th century, and commercial cultivation began in the U. S. and Canada to supply the increased demand. In 1950, James and Gerald Godward started experimenting with wild rice in a meadow north of Brainerd
Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the group on the periodic table and is a highly reactive nonmetal. By mass, oxygen is the third-most abundant element in the universe, after hydrogen, at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. This is an important part of the atmosphere and diatomic oxygen gas constitutes 20. 8% of the Earths atmosphere, additionally, as oxides the element makes up almost half of the Earths crust. Most of the mass of living organisms is oxygen as a component of water, oxygen is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide. Oxygen is too reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, strongly absorbs ultraviolet UVB radiation, but ozone is a pollutant near the surface where it is a by-product of smog.
At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft, the name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle, Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries Leonardo da Vinci built on Philos work by observing that a portion of air is consumed during combustion and respiration, Oxygen was discovered by the Polish alchemist Sendivogius, who considered it the philosophers stone. In the late 17th century, Robert Boyle proved that air is necessary for combustion, English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus.
From this he surmised that nitroaereus is consumed in both respiration and combustion, Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract De respiratione. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, one part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the combustion products
Eichhornia crassipes, commonly known as water hyacinth, is an aquatic plant native to the Amazon basin, and is often a highly problematic invasive species outside its native range. Water hyacinth is a perennial aquatic plant native to tropical and sub-tropical South America. With broad, glossy, ovate leaves, water hyacinth may rise above the surface of the water as much as 1 meter in height, the leaves are 10–20 cm across, and float above the water surface. They have long and bulbous stalks, the feathery, freely hanging roots are purple-black. An erect stalk supports a single spike of 8-15 conspicuously attractive flowers, when not in bloom, water hyacinth may be mistaken for frogs-bit. One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or stolons, each plant additionally can produce thousands of seeds each year, and these seeds can remain viable for more than 28 years. Some water hyacinths were found to grow up to 2 to 5 metres a day in some sites in Southeast Asia, the common water hyacinth are vigorous growers known to double their population in two weeks.
In their native range these flowers are pollinated by long tongued bees, the invasiveness of the hyacinth is related to its ability to clone itself and large patches are likely to all be part of the same genetic form. There are three morphs of water hyacinth, long medium and short, the short morph is restricted to the native range due to founder events during its distribution. Its habitat ranges from desert to subtropical or warm temperate desert to rainforest zones.0 to 7.5. It does not tolerate water temperatures >35 °C, leaves are killed by frost and salt water, the latter trait being used to kill some of it by floating rafts of the cut weed to the sea. Water hyacinths do not grow when the salinity is greater than 15% that of sea water. In brackish water, its leaves show epinasty and chlorosis, because of E. Neochetina eichhorniae causes a substantial reduction in water hyacinth production, it reduces plant height, root length, and makes the plant produce fewer daughter plants. N. eichhorniae was introduced from Argentina to Florida in 1972, a semi-aquatic grasshopper, Cornops aquaticum, is being investigated in South Africa as an additional control agent.
Azotobacter chroococcum, an N-fixing bacteria, is concentrated around the bases of the petioles. But the bacteria do not fix nitrogen unless the plant is suffering extreme N-deficiency and this plant is reported to contain HCN, and triterpenoid, and may induce itching. Plants sprayed with 2, 4-D may accumulate lethal doses of nitrates, Water hyacinth has been widely introduced in North America, Asia, Australia and New Zealand. In many areas it is has become an important and pernicious invasive species, in New Zealand it is listed on the National Pest Plant Accord which prevents it from being propagated, distributed or sold
Carex is a vast genus of almost 2,000 species of grassy plants in the family Cyperaceae, commonly known as sedges. Other members of the Cyperaceae family are called sedges, however those of genus Carex may be called true sedges, the study of Carex is known as caricology. All species of Carex are perennial, although some species, such as C. bebbii and C. viridula can fruit in their first year of growth and they typically have rhizomes, stolons or short rootstocks, but some species grow in tufts. The culm – the flower-bearing stalk – is unbranched and usually erect and it is usually distinctly triangular in section. The leaves of Carex comprise a blade, which away from the stalk, and a sheath. The blade is long and flat, but may be folded, channelled or absent. The leaves have parallel veins and a distinct midrib, where the blade meets the culm there is a structure called the ligule. The colour of foliage may be green, red or brown, the flowers of Carex are small and are combined into spikes, which are themselves combined into a larger inflorescence.
The spike typically contains many flowers, but can hold as few as one in some species, almost all Carex species are monoecious, each flower is either male or female. Sedges exhibit diverse arrangements of male and female flowers, the lower spikes are entirely pistillate and upper spikes staminate, with one or more spikes in between having pistillate flowers near the base and staminate flowers near the tip. In other species, all spikes are similar, in that case, they may have male flowers above and female flowers below or female flowers above and male flowers below. In relatively few species, the arrangement of flowers is irregular, the defining structure of the genus Carex is the bottle-shaped bract surrounding each female flower. This structure is called the perigynium or utricle, a modified prophyll and it is typically extended into a rostrum or beak, which is often divided at the tip into two teeth. The shape and vestiture of the perigynium are important structures for distinguishing Carex species, the fruit of Carex is a dry, one-seeded indehiscent achene or nut which grows within the perigynium.
Perigynium features aid in fruit dispersal, Carex species are found across most of the world, albeit with few species in tropical lowlands, and relatively few in sub-Saharan Africa. Most sedges are found in wetlands – such as marshes, calcareous fens and other peatlands and stream banks, riparian zones, and even ditches. They are one of the dominant plant groups in arctic and alpine tundra, the genus Carex was established by Carl Linnaeus in his work Species Plantarum in 1753, and is one of the largest genera of flowering plants. Estimates of the number of species vary from about 1100 to almost 2000, Carex displays the most dynamic chromosome evolution of all flowering plants
Victoria amazonica is a species of flowering plant, the largest of the Nymphaeaceae family of water lilies. The species has large leaves, up to 3 m in diameter. The species was once called Victoria regia after Queen Victoria, V. amazonica is native to the shallow waters of the Amazon River basin, such as oxbow lakes and bayous. It is depicted in the Guyanese coat of arms, the flowers are white the first night they are open and become pink the second night. They are up to 40 cm in diameter, and are pollinated by beetles and this process was described in detail by Sir Ghillean Prance and Jorge Arius. It is the largest waterlily in the world. A member of the genus Victoria placed in the Nymphaeaceae family or, the first published description of the genus was by John Lindley in October 1837, based on specimens of this plant returned from British Guiana by Robert Schomburgk. Lindley named the genus after the newly ascended Queen Victoria, the spelling in Schomburgks description in Athenaeum, published the month before, was given as Victoria Regina.
Despite this spelling being adopted by the Botanical Society of London for their new emblem, an earlier account of the species, Euryale amazonica by Eduard Friedrich Poeppig, in 1832 described an affinity with Euryale ferox. A collection and description was made by the French botanist Aimé Bonpland in 1825. In 1850 James De Carle Sowerby recognised Poeppigs earlier description and transferred its epithet amazonica, the new name was rejected by Lindley. The current name, Victoria amazonica, did not come into use until the twentieth century. Victoria regia, as it was named, was discovered by Tadeáš Haenke in 1801 and it was once the subject of rivalry between Victorian gardeners in England. The species captured the imagination of the public, and was the subject of several dedicated monographs, the botanical illustrations of cultivated specimens in Fitch and W. J. Hookers 1851 work Victoria Regia received critical acclaim in the Athenaeum, they are accurate, and they are beautiful. The Duke of Devonshire presented Queen Victoria with one of the first of these flowers, the lily, with ribbed undersurface and leaves veining like transverse girders and supports, was Paxtons inspiration for The Crystal Palace, a building four times the size of St.
Peters in Rome
Duckweed, or water lens, are flowering aquatic plants which 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, classifications created prior to the end of the 20th century classify them as a separate family, Lemnaceae. These plants are simple, lacking an obvious stem or leaves. The greater part of plant is a small organized thallus or frond structure only a few cells thick. Depending on the species, each plant may have no root or may have one or more simple rootlets, reproduction is mostly by asexual budding, 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 sexual reproduction occurs. Some view this flower as a pseudanthium, or reduced inflorescence, 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, the fruit produced through this occasional sexual reproduction is a utricle, and a seed is produced in a sac containing air that facilitates flotation. One of the important factors influencing the distribution of wetland plants. Duckweeds tend to be associated with fertile, even eutrophic conditions and they can be spread by waterfowl and small mammals, transported inadvertently on their feet and bodies, as well as by moving water. In water bodies with constant currents or overflow, the plants are carried down the water channels, in some locations, a cyclical pattern driven by weather patterns exists in which the plants proliferate greatly during low water-flow periods, are carried away as rainy periods ensue. Duckweed is an important high-protein food source for waterfowl and is eaten by humans in some parts of Southeast Asia, as it contains more protein than soybeans, it is sometimes cited as a significant potential food source.
The tiny plants provide cover for fry of many aquatic species, the plants are used as shelter by pondwater species such as bullfrogs and fish such as bluegills. They provide shade and, although confused with them. For these reasons, they are touted as water purifiers of untapped value, the same publication provides an extensive list of references for many duckweed-related topics. These plants may play a role in conservation of water because a cover of duckweed will reduce evaporation of water compared to the rate of a similarly sized water body with a clear surface. The duckweeds have long been a mystery, and usually have been considered to be their own family. Flowers, if present at all, are small, roots are either very much reduced, or absent entirely
Cyperus papyrus is a species of aquatic flowering plant belonging to the sedge family Cyperaceae. It is a herbaceous perennial, native to Africa. Papyrus sedge has a long history of use by humans, notably by the Ancient Egyptians—it is the source of papyrus paper. Parts of the plant can be eaten, and the highly buoyant stems can be made into boats and it is now often cultivated as an ornamental plant. In nature, it grows in sun, in flooded swamps, and on lake margins throughout Africa, Madagascar. C. papyrus and the dwarf cultivar C. papyrus Nanus have gained the Royal Horticultural Societys Award of Garden Merit and this tall, leafless aquatic plant can grow 4 to 5 m high. It forms a clump of triangular green stems that rise up from thick. Each stem is topped by a cluster of thin, bright green, thread-like stems around 10 to 30 cm in length. Greenish-brown flower clusters eventually appear at the ends of the rays, giving way to brown, the younger parts of the rhizome are covered by red-brown, triangular scales, which cover the base of the culms.
Botanically, these represent reduced leaves, so strictly it is not quite correct to call this plant fully leafless, Egyptians used the plant for many purposes, most famously for making papyrus. Its name in Greek and in English is widely believed to have come from Egyptian, Cyperus papyrus is now used mainly for decoration, as it is nearly extinct in its native habitat in the Nile Delta, where in ancient times it was widely cultivated. Theophrastus History of Plants states that it grew in Syria, and according to Plinys Natural History, it was a plant of the Niger River. Aside from papyrus, several members of the genus Cyperus may have been involved in the multiple uses Egyptians found for the plant. Its flowering heads were linked to make garlands for the gods in gratitude, the pith of young shoots was eaten both cooked and raw. Its woody root made bowls and other utensils and was burned for fuel, from the stems were made reed boats, mats, cloth and sandals. The rush or reed basket in which the Biblical figure Moses was abandoned may have made from papyrus.
The adventurer Thor Heyerdahl built two boats from papyrus, Ra and Ra II, in an attempt to demonstrate that ancient African or Mediterranean people could have reached America and he succeeded in sailing Ra II from Morocco to Barbados. Fishermen in the Okavango Delta use small sections of the stem as floats for their nets, papyrus can be found in tropical rain forests, tolerating annual temperatures of 20 to 30 °C and a pH of 6.0 to 8.5
Sagittaria is a genus of about 30 species of aquatic plants whose members go by a variety of common names, including arrowhead, duck potato, Omodaka, swamp potato, tule potato, and wapato. Most are native to South and North America, but there are some from Europe, Africa. One of the names for plant is derived from the edible underwater tuber that the plant produces. In late fall or early spring, disturbing the aquatic mud in which the plant grows will cause its small tubers to float to the surface where they can be harvested, accepted species, Sagittaria aginashii Makino - Japan, Primorye Sagittaria ambigua J. G. Sm. – Wapato, Northern Arrowhead, Swamp Potato - most of Canada including Yukon and Northwest Territories, Alaska, – Chihuahuan arrowhead - New Mexico, northeastern Mexico Sagittaria engelmanniana J. G. Sm. – Engelmanns arrowhead - eastern US from Mississippi to Vermont Sagittaria fasciculata E. O. Beal – Bunched Arrowhead - North and South Carolina Sagittaria filiformis J. G. Sm. – Threadleaf Arrowhead - eastern US from Alabama to Maine Sagittaria graminea Michx. L. P. P.
de Candolle & A. C. P. de Candolle - Greater Antilles, Colombia, – Large-fruited Arrowhead - North and South Carolina Sagittaria macrophylla Zucc. – Papa de agua - Mexico Sagittaria montevidensis Cham, – California Arrowhead – widespread across much of USA, Mexico and South America Sagittaria natans Pall. Agostini - Brazil, Venezuela Sagittaria platyphylla J. G. Sm. - southern China Sagittaria pygmaea Miq, – Pygmy arrowhead - China, Korea, Thailand, Vietnam Sagittaria rhombifolia Cham. Wiesneria triandra Micheli Rataj, K. Annot,76, 1–31,78, 1–61 Staff of the L. H. Bailey Hortorium, Hortus Third, pg.993 Plants for a Future The Arrowheads Edibility of Sagittaria and edible parts of Sagittaria
Seagrasses are flowering plants belonging to four families, all in the order Alismatales, which grow in marine, fully saline environments. There are 12 genera with some 60 species known, like all autotrophic plants, seagrasses photosynthesize so are limited to growing in the submerged photic zone, and most occur in shallow and sheltered coastal waters anchored in sand or mud bottoms. Most species undergo submarine pollination and complete their life cycle underwater. Seagrasses form extensive beds or meadows, which can be either monospecific or in mixed beds where more than one species coexist. In temperate areas, usually one or a few species dominate, whereas tropical beds usually are more diverse, some fish species that visit/feed on seagrasses raise their young in adjacent mangroves or coral reefs. Also, seagrasses trap sediment and slow down water movement, causing suspended sediment to fall out, the trapping of sediment benefits coral by reducing sediment loads in the water. Their importance for associated species is due to provision of shelter.
Seagrass meadows account for more than 10% of the total carbon storage. Per hectare, it twice as much carbon dioxide as rain forests. Yearly, seagrasses sequester about 27.4 million tons of CO2, global warming models suggest, some seagrasses will go extinct – Posidonia oceanica is expected to go extinct, or nearly so, by 2050. This would result in CO2 release, seagrasses were collected as fertilizer for sandy soil. This was an important use in the Ria de Aveiro, Portugal and it was used for bandages and other purposes. Currently, seagrass is used in furniture, and woven like rattan, natural disturbances, such as grazing, ice-scouring, and desiccation, are an inherent part of seagrass ecosystem dynamics. Seagrasses display a high degree of phenotypic plasticity, adapting rapidly to changing environmental conditions. Seagrasses are in decline, with some 30,000 km2 lost during recent decades. The main cause is human disturbance, most notably eutrophication, mechanical destruction of habitat, excessive input of nutrients is directly toxic to seagrasses, but most importantly, it stimulates the growth of epiphytic and free-floating macro- and micro-algae.
This weakens the sunlight, reducing the photosynthesis that nourishes the seagrass, decaying seagrass leaves and algae fuels increasing algal blooms, resulting in a positive feedback. This can cause a regime shift from seagrass to algal dominance
Soil is a mixture of minerals, organic matter, gases and countless organisms that together support life on Earth. Soil is called the Skin of the Earth and interfaces with the lithosphere, the hydrosphere, the atmosphere, the term pedolith, used commonly to refer to the soil, literally translates ground stone. Soil consists of a phase of minerals and organic matter, as well as a porous phase that holds gases. Accordingly, soils are often treated as a system of solids, liquids. Soil is a product of the influence of climate, organisms, Soil continually undergoes development by way of numerous physical and biological processes, which include weathering with associated erosion. Given its complexity and strong internal connectedness soil has been considered as an ecosystem by soil ecologists. Most soils have a dry bulk density between 1.1 and 1.6 g/cm3, while the particle density is much higher. Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic, Soil science has two basic branches of study and pedology.
Edaphology is concerned with the influence of soils on living things, pedology is focused on the formation and classification of soils in their natural environment. In engineering terms, soil is referred to as regolith, or loose material that lies above the solid geology. Soil is commonly referred to as earth or dirt, technically, as soil resources serve as a basis for food security, the international community advocates its sustainable and responsible use through different types of soil governance. Soil is a component of the Earths ecosystem. The worlds ecosystems are impacted in far-reaching ways by the carried out in the soil, from ozone depletion and global warming, to rainforest destruction. Following the atmosphere, the soil is the next largest carbon reservoir on Earth, as the planet warms, soils will add carbon dioxide to the atmosphere due to its increased biological activity at higher temperatures. Thus, soil carbon losses likely have a positive feedback response to global warming.
Since soil has a range of available niches and habitats. A gram of soil can contain billions of organisms, belonging to thousands of species, mostly microbial, Soil has a mean prokaryotic density of roughly 108 organisms per gram, whereas the ocean has no more than 107 procaryotic organisms per milliliter of seawater. Since plant roots need oxygen, ventilation is an important characteristic of soil and this ventilation can be accomplished via networks of interconnected soil pores, which absorb and hold rainwater making it readily available for plant uptake
Insects are a class of hexapod invertebrates within the arthropod phylum that have a chitinous exoskeleton, a three-part body, three pairs of jointed legs, compound eyes and one pair of antennae. They are the most diverse group of animals on the planet, including more than a million described species, the number of extant species is estimated at between six and ten million, and potentially represent over 90% of the differing animal life forms on Earth. Insects may be found in all environments, although only a small number of species reside in the oceans. The life cycles of insects vary but most hatch from eggs, insect growth is constrained by the inelastic exoskeleton and development involves a series of molts. The immature stages can differ from the adults in structure and habitat, Insects that undergo 3-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages. The higher level relationship of the Hexapoda is unclear, fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm.
The most diverse insect groups appear to have coevolved with flowering plants, adult insects typically move about by walking, flying or sometimes swimming. As it allows for rapid yet stable movement, many insects adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles, Insects are the only invertebrates to have evolved flight. Many insects spend at least part of their lives under water, with adaptations that include gills. Some species, such as water striders, are capable of walking on the surface of water, Insects are mostly solitary, but some, such as certain bees and termites, are social and live in large, well-organized colonies. Some insects, such as earwigs, show maternal care, guarding their eggs, Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over great distances, other species communicate with sounds, crickets stridulate, or rub their wings together, to attract a mate and repel other males.
Lampyridae in the beetle order communicate with light, humans regard certain insects as pests, and attempt to control them using insecticides and a host of other techniques. Some insects damage crops by feeding on sap, leaves or fruits, a few parasitic species are pathogenic. Some insects perform complex ecological roles, blow-flies, for example, help consume carrion, Many other insects are considered ecologically beneficial as predators and a few provide direct economic benefit. Silkworms and bees have been used extensively by humans for the production of silk and honey, in some cultures, people eat the larvae or adults of certain insects. Insect first appears documented in English in 1601 in Hollands translation of Pliny, translations of Aristotles term form the usual word for insect in Welsh, Serbo-Croatian, etc. The evolutionary relationship of insects to other animal groups remains unclear, in the Pancrustacea theory, together with Entognatha and Cephalocarida, make up a natural clade labeled Miracrustacea
Pistia is a genus of aquatic plant in the arum family, Araceae. The single species it comprises, Pistia stratiotes, is called water cabbage, water lettuce, Nile cabbage. Its native distribution is uncertain, but probably pantropical, it was first discovered from the Nile near Lake Victoria in Africa and it is now present, either naturally or through human introduction, in nearly all tropical and subtropical fresh waterways. The genus name is derived from the Greek word πιστός, meaning water and it is a perennial monocotyledon with thick, soft leaves that form a rosette. It floats on the surface of the water, its roots hanging submersed beneath floating leaves, the leaves can be up to 14 cm long and have no stem. They are light green, with veins, wavy margins and are covered in short hairs which form basket-like structures which trap air bubbles. The flowers are dioecious, and are hidden in the middle of the plant amongst the leaves, small green berries form after successful fertilization. The plant can undergo asexual reproduction and daughter plants are connected by a short stolon, forming dense mats.
Water lettuce is among the worlds most productive freshwater aquatic plants, in waters with high nutrient content, particularly those that have been contaminated with human loading of sewage or fertilizers, water lettuce can often exhibit weedy overgrowth behavior. It may commonly become weedy in hydrologically altered systems such as canals and it is a common aquatic plant in the southeast United States, particularly in Florida. Severe overgrowth of water lettuce can block gas exchange at the interface, reducing the oxygen in the water. Large mats can light, shade native submerged plants. Mosquitoes of the genus Mansonia complete their life cycle only in the presence of plants such as Pistia. The emerging larvae fall into the water within 24 hours and stay attached to the Pistia root with the help of a siphon tube for respiration. The pupa is attached to the pistia root with the serrated piercing siphon tube. The egg to adult mosquito development is completed within 7 days, Pistia can be controlled by mechanical harvesters that remove the water lettuce from the water and transport it to disposal on shore.
Aquatic herbicides may be used, two insects are being used as a biological control. Adults and larvae of the South American weevil Neohydronomous affinis feed on Pistia leaves, both are proving to be useful tools in the management of Pistia