Pistia
Encyclopedia
Pistia is a genus of aquatic plant
in the arum
family, Araceae
. The single species it comprises, Pistia stratiotes, is often called water cabbage, water lettuce, or Nile cabbage. Its native distribution is uncertain, but probably pantropical
; it was first described from the Nile
near Lake Victoria
in Africa
. 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 (pistos), meaning "water," and refers to the aquatic nature of the plants.
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 parallel veins, wavy margins and are covered in short hairs which form basket-like structures which trap air bubbles, increasing the plant's buoyancy. The flower
s are dioecious
, and are hidden in the middle of the plant amongst the leaves. Small green berries form after successful fertilization. The plant can also undergo asexual reproduction
. Mother and daughter plants are connected by a short stolon
, forming dense mats.
in waterways. It is a common aquatic weed in the United States
, particularly in Florida
where it may clog waterways. It has the potential to reduce the biodiversity of a waterway. Mats of Pistia block gas exchange at the air-water interface, reducing the oxygen in the water and killing fish
. They also block light, killing native submerged plants, and alter immersed plant communities by crushing them.
Mosquitoes of the genus Mansonioides complete their life cycle only in the presence of aquatic plants such as Pistia, laying their eggs under the leaves. The emerging larvae fall into the water within 24 hours and stay attached to the Pistia root (which is rich with air sacs) with the help of a serrated siphon tube for respiration and develop into pupa. The pupa is also attached to the pistia root with the serrated piercing siphon tube. The egg to adult mosquito development is completed within 7 days.
s are also being used as a biological control. Adults and larvae of the South America
n weevil
Neohydronomous affinis feed on Pistia leaves, and the larvae of moth Spodoptera pectinicornis
from Thailand
. Both are proving to be useful tools in the management of Pistia.
Aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...
in the arum
Arum
Arum is a genus of about 25 species of flowering plants in the family Araceae, native to Europe, northern Africa, and western Asia, with the highest species diversity in the Mediterranean region....
family, Araceae
Araceae
Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe or leaf-like bract. Also known as the Arum family, members are often colloquially...
. The single species it comprises, Pistia stratiotes, is often called water cabbage, water lettuce, or Nile cabbage. Its native distribution is uncertain, but probably pantropical
Pantropical
In biogeography, a pantropical distribution one which covers tropical regions of all of the major continents, i.e. in Africa, in Asia and in the Americas. Examples include the plant genera Acacia and Bacopa....
; it was first described from the Nile
Nile
The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...
near Lake Victoria
Lake Victoria
Lake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. 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
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word πιστός (pistos), meaning "water," and refers to the aquatic nature of the plants.
Description
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...
monocotyledon
Monocotyledon
Monocotyledons, also known as monocots, are one of two major groups of flowering plants that are traditionally recognized, the other being dicotyledons, or dicots. Monocot seedlings typically have one cotyledon , in contrast to the two cotyledons typical of dicots...
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 parallel veins, wavy margins and are covered in short hairs which form basket-like structures which trap air bubbles, increasing the plant's buoyancy. The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are dioecious
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....
, and are hidden in the middle of the plant amongst the leaves. Small green berries form after successful fertilization. The plant can also undergo asexual reproduction
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
. Mother and daughter plants are connected by a short stolon
Stolon
In biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.-In botany:...
, forming dense mats.
Ecology
The growth habit can make it a weedWeed
A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...
in waterways. It is a common aquatic weed in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, particularly in Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
where it may clog waterways. It has the potential to reduce the biodiversity of a waterway. Mats of Pistia block gas exchange at the air-water interface, reducing the oxygen in the water and killing fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
. They also block light, killing native submerged plants, and alter immersed plant communities by crushing them.
Mosquitoes of the genus Mansonioides complete their life cycle only in the presence of aquatic plants such as Pistia, laying their eggs under the leaves. The emerging larvae fall into the water within 24 hours and stay attached to the Pistia root (which is rich with air sacs) with the help of a serrated siphon tube for respiration and develop into pupa. The pupa is also attached to the pistia root with the serrated piercing siphon tube. The egg to adult mosquito development is completed within 7 days.
Control
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 also be used. Two insectInsect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s are also being used as a biological control. Adults and larvae of the South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n weevil
Weevil
A weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
Neohydronomous affinis feed on Pistia leaves, and the larvae of moth Spodoptera pectinicornis
Spodoptera pectinicornis
The Waterlettuce Moth is a moth of the Noctuidae family. It is native to Asia, where it can be found from the North-eastern parts of the Himalaya to Sundaland and in New Guinea...
from Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
. Both are proving to be useful tools in the management of Pistia.
Uses
Water lettuce is often used in tropical aquariums to provide cover for fry and small fish. It is also helpful as it outcompetes algae for nutrients in the water, thereby preventing massive algal blooms.External links
- Centre for Aquatic and Invasive Plants
- Thai flora in literature
- Pistia stratiotes information from the Hawaiian Ecosystems at Risk project (HEAR)
- Species Profile- Water Lettuce (Pistia stratiotes), National Invasive Species Information Center, United States National Agricultural LibraryUnited States National Agricultural LibraryThe United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...
. Lists general information and resources for Water Lettuce.