Pontederia crassipes
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.
Description
Water hyacinth is a free-floating perennial aquatic plant native to tropical and subtropical South America. With broad, thick, glossy, ovate leaves, water hyacinth may rise above the surface of the water as much as in height. The leaves are across on a stem, which is floating by means of buoyant bulb-like nodules at its base above the water surface. They have long, spongy, bulbous stalks. The feathery, freely hanging roots are purple-black. An erect stalk supports a single spike of 8–15 conspicuously attractive flowers, mostly lavender to pink in colour with six petals. When not in bloom, water hyacinth may be mistaken for frogbit or Amazon frogbit.One of the fastest-growing plants known, water hyacinth reproduces primarily by way of runners or stolons, which eventually form daughter plants. Each plant additionally can produce thousands of seeds each year, and these seeds can remain viable for more than 28 years. Common water hyacinths are vigorous growers, and mats can double in size in one to two weeks. In terms of plant count rather than size, they are said to multiply by more than a hundredfold in number in a matter of 23 days.
In their native range, the flowers are pollinated by long-tongued bees, and the plants can reproduce both sexually and clonally. 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.
Water hyacinth has three flower morphs and is termed "tristylous". The flower morphs are named for the length of their pistils: long, medium, and short. Tristylous populations are, however, limited to the native lowland South American range of water hyacinth; in the introduced range, the M-morph prevails, with the L-morph occurring occasionally and the S-morph absent altogether. This geographical distribution of the floral morphs indicates that founder events have played a prominent role in the species' worldwide spread.
Habitat and ecology
Its habitat ranges from tropical desert to subtropical or warm, temperate desert to rainforest zones. The temperature tolerance of the water hyacinth is:- Its minimum growth temperature is
- Its optimum growth temperature is
- Its maximum growth temperature is
Azotobacter chroococcum, a species of nitrogen-fixing bacteria, is probably concentrated around the bases of the petioles, but the bacteria do not fix nitrogen unless the plant is suffering extreme nitrogen deficiency.
Fresh plants contain prickly crystals. This plant is reported to contain hydrogen cyanide, alkaloids, and triterpenoids, and may induce itching. Plants sprayed with 2,4-dichlorophenoxyacetic acid may accumulate lethal doses of nitrates and other harmful elements in polluted environments.
Invasive species
Water hyacinth grows and reproduces quickly, so it can cover large portions of ponds and lakes. It can easily coexist with other invasive plants and native plants in an area. Particularly vulnerable are bodies of water that have already been affected by human activities, such as artificial reservoirs or eutrophied lakes that receive large amounts of nutrients. It outcompetes native aquatic plants, both floating and submerged. In 2011, Wu Fuqin et al. tracked the results of Yunnan Dianchi Lake and also showed that water hyacinth could affect the photosynthesis of phytoplankton, submerged plants, and algae by water environment quality and inhibit their growth. The decay process depletes dissolved oxygen in the water, often killing fish.Water hyacinth can absorb a large amount of harmful heavy metals and other substances. After death, it rots and sinks to the bottom of the water, causing secondary pollution to the water body, destroying the natural water quality, and may even affect the quality of residents' drinking water in severe cases. Water where water hyacinth grows heavily is often a breeding place for disease vectors and harmful pathogens, posing a potential threat to the health of local residents. It is very critical to monitor areas quickly that are infested in order to efficiently reduce or control the growth of these species. Water hyacinth can also provide a food source for goldfish, keep water clean, and help with oxygenation. Invertebrate species harboring with water hyacinth are dispersed as phytochores.
The invasion of water hyacinth also has socioeconomic consequences. Since water hyacinth is composed of up to 95% water, its evapotranspiration rate is high. As such, small lakes that have been covered with the species can dry out and leave communities without adequate water or food supply. In some areas, dense mats of water hyacinth prevent the use of a waterway, leading to the loss of transportation, as well as a loss of fishing possibilities. Large sums of money are allocated to the removal of water hyacinth from the water bodies as well as figuring out how to destroy the remains harvested. Harvesting water hyacinth mechanically requires considerable effort. A million tons of fresh biomass would require 75 trucks with a capacity of 40 m3, per day, for 365 days to get rid of it. The water hyacinth would then be transferred to a dumping site and allowed to decompose, which releases CO2, methane, and nitrogen oxides.
Water hyacinth has been widely introduced in North America, Europe, Asia, Australia, Africa, and New Zealand. In many areas, it 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. In large water areas such as Louisiana, the Kerala Backwaters in India, Tonlé Sap in Cambodia, and Lake Victoria, it has become a serious pest. The common water hyacinth has become an invasive plant species on Lake Victoria in Africa after it was introduced into the area in the 1980s.
A 1.22 Gb/8 chromosome reference genome was assembled to study nuclear and chloroplast genomes between 10 water hyacinth lines from 3 continents. Results indicate the spread of a limited genotype of water hyacinth from South America, where it has the highest genetic diversity. The paper proposes the spread potentially originating from ships travelling from Itajaí Port on the Brazilian East Coast. However, genetic studies on samples from Bangladesh and Indonesia demonstrate different genotypes, potentially implicating multiple introduction vectors.
Further, the genomic study also revealed the adaptation in four key pathways; plant-pathogen interaction, plant-hormone signal transduction, photosynthesis and abiotic stress tolerance, which provide water hyacinth to expand its niche and compete with other native flora.
United States
Introduction into the U.S.
Various accounts are given as to how the water hyacinth was introduced to the United States.The claim that the water hyacinth was introduced to the U.S. in 1884 at the World's Fair in New Orleans, also known as the World Cotton Centennial, has been characterized as the "first authentic account", as well as "local legend".
At some point, a legend arose that the plants had been given away as a gift by a Japanese delegation at the fair. This claim is absent in a pertinent article published in a military engineer's trade journal dating to 1940, but appears in a piece penned in 1941 by the director of the wildlife and fisheries division at the Louisiana Department of Conservation, where the author writes, "the Japanese government maintained a Japanese building" at the fair, and the "Japanese staff imported from Venezuela considerable numbers of water hyacinth, which were given away as souvenirs". The claim has been repeated by later writers, with various shifts in the details. Thus National Academy of Sciences fellow Noel D. Vietmeyer wrote that "Japanese entrepreneurs" introduced the plant into the U.S., and the plants had been "collected from the Orinoco River in Venezuela." This claim was echoed by a pair of NASA researchers, who asserted that the souvenir plants were carelessly dumped in various waterways. Canadian biologist Spencer C. H. Barrett meanwhile favored the theory they were first cultivated in garden ponds, after which they multiplied and escaped to the environs. The account gains different details as told by children's story-teller Carole Marsh, who says "Japan gave away water hyacinth seeds" during the exposition, and another Southern raconteur, Gaspar J. "Buddy" Stall, assured his readership that the Japanese gave each family a package of those seeds.
One paper has also inquired into the role which catalog sales of seeds and plants may have played in the dissemination of invasive plants. P. crassipes was found to have been offered in the 1884 issue of Bordentown, New Jersey–based Edmund D. Sturtevant's Catalogue of Rare Water Lilies and Other Choice Aquatic Plants, and of Germany has offered the plant since 1864. By 1895, it was offered by seed purveyors in the states of New Jersey, New York, California, and Florida.
Harper's Weekly magazine printed an anecdotal account stating that a certain man from New Orleans collected and brought home water hyacinths from Colombia, around 1892, and the plant proliferated in a matter of 2 years.