Water hyacinth
| Water Hyacinth | |
|---|---|
 | |
| Common Water Hyacinth (E. crassipes) | |
| Scientific classification | |
| Kingdom: | Plantae |
| Phylum: | Angiosperms |
| Class: | Monocotyledoneae |
| Order: | Commelinales |
| Family: | Pontederiaceae |
| Genus: | Eichhornia Kunth |
| Species | |
|
Seven species, including: | |
The seven species of water hyacinth constitute the genus Eichhornia.
Contents
[show]Description
Water hyacinth is a free-floating perennial aquatic plant(or hydrophyte) native to tropical and sub-tropical South America. With broad, thick, 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, spongy and 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 frog's-bit (Limnobium spongia).
One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or stolons, which eventually form daughter plants. Each plant can produce thousands of seeds each year, and these seeds can remain viable for more than 28 years.[1] The common water hyacinth (Eichhornia crassipes) are vigorous growers known to double their population in two weeks.
Invasiveness as an exotic plant
Water hyacinth has been widely introduced in North America, Asia, Australia, Africa and New Zealand. They can be found in large water areas such as Louisiana, or in the Kerala Backwaters in India. In many areas it, particularly E. crassipes, is an important and pernicious invasive species. First introduced to North America in 1884, an estimated 50 kilograms per square metre of hyacinth once choked Florida's waterways,[2] although the problem there has since been mitigated.[citation needed] When not controlled, water hyacinth will cover lakes and ponds entirely; this dramatically impacts water flow, blocks sunlight from reaching native aquatic plants, and starves the water of oxygen, often killing fish (or turtles). The plants also create a prime habitat for mosquitos[citation needed], the classic vectors of disease, and a species of snail known to host a parasitic flatworm which causes schistosomiasis (snail fever)[citation needed]. Directly blamed for starving subsistence farmers in Papua New Guinea[citation needed], water hyacinth remains a major problem where effective control programs are not in place. Water hyacinth is often problematic in man-made ponds if uncontrolled, but can also provide a food source for gold fish, keep water clean [3] [4] and help to provide oxygen[citation needed] to man-made ponds.
Water hyacinth often invades bodies of water that have been impacted by human activities[citation needed]. For example, the plants can unbalance natural lifecycles in artificial reservoirs or in eutrophied lakes that receive large amounts of nutrients.
Eichhornia crassipes, 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[citation needed].
Control
Water hyacinth can be controlled using three methods:
- Chemical Control
The application of herbicides for controlling water hyacinth has been carried out for many years and it has been found that there is a good success rate when dealing with small infestations. A main concern when using herbicides is the environmental and health related effects, especially where people collect water for drinking and washing.
- Physical Control
Physical control is performed by land based machines such as bucket cranes, draglines, or boorm or by water based machinery such as aquatic weed harvester, dredges, or vegetation shredders. Mechanical removal is seen as the best short-term solution to the proliferation of the plant. A project on Lake Victoria in Africa used various pieces of equipment to chop, collect, and dispose of 1500 hectares of water hyacinth in a 12 month period. It is however costly and requires the use of both land and water vehicles, but it took many years for the lake to become in poor condition and reclamation will be a continual process.
- Biological Control
As chemical and mechanical removal is often too expensive and ineffective, researchers have turned to biological control agents to deal with water hyacinth. The effort began in the 1970s when USDA researchers released three species of weevil known to feed on water hyacinth into the United States, Neochetina bruchi, N. eichhorniae, and the water hyacinth borer Sameodes albiguttalis. Although meeting with limited success, the weevils have since been released in more than 20 other countries. However, the most effective control method remains the control of excessive nutrients and prevention of the spread of this species.
May 2010 the USDA’s Agricultural Research Service released Megamelus scutellaris as a biological control insect for the invasive waterhyacinth species. Megamelus scutellaris is a small planthopper insect native to Argentina. Researchers have been studying the effects of the biological control agent in extensive host-range studies since 2006 and concluded that the insect is highly host-specific and will not pose a threat to any other plant population other than the targeted water hyacinth. Researchers also hope that the biological control will be more resilient than existing biological controls to the herbicides that are already in place to combat the invasive water hyacinth. [2]
Uses
Since the water hyacinths are so prolific, harvesting them for industrial use serves also as a means of environmental control.
In the Philippines, Thailand and Vietnam the water hyacinth's stems are used as a braiding material and a source of fibers. Strings of dried fibers are woven or interlinked together to form a braid or cord used for making bags, footwear, wreaths, hats, vases, Christmas lanterns, and more decorative materials. Dried stems are used for baskets and furniture. Water hyacinth fibers are used as a raw material for paper.
Since the plant has abundant nitrogen content, it can be used a substrate for biogas production and the sludge obtained from the biogas. However, due to easy accumulation of toxins, the plant is prone to get contaminated when used as feed.
The plant is extremely tolerant of, and has a high capacity for, the uptake of heavy metals, including Cd, Cr, Co, Ni, Pb and Hg, which could make it suitable for the biocleaning of industrial wastewater [5], [6], [7],.[8] In addition to heavy metals, Eichhornia crassipes can also remove other toxins, such as cyanide, which is environmentally beneficial in areas that have endured gold mining operations.[9]
Water hyacinth removes arsenic from arsenic contaminated drinking water. It may be a useful tool in removing arsenic from tube well water in Bangladesh.[10]
Water hyacinth is also observed to enhance nitrification in waste water treatment cells of living technology. Their root zones are superb micro-sites for bacterial communities.[11]
Water hyacinth is a common fodder plant in the third world especially Africa though excessive use can be toxic. It is high in protein (nitrogen) and trace minerals and the goat feces are a good source of fertilizer as well.
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