Zizania texana
Encyclopedia
Zizania texana is a rare species of grass
known by the common name Texas wild rice. It is endemic to Texas
, where it is found only on the upper San Marcos River
in Hays County
. It is threatened by the loss and degradation of its habitat. It is a federally listed endangered species
of the United States.
This grass, a member of the same genus as commercially sold wild rice
, is an aquatic plant
that grows in the water with only its stem tips rising above the surface. It grows 1 to 2 meters long but the stems have been known to reach five meters in length. The ribbon-like leaves are up to a meter in length. The inflorescence
is a panicle
up to 31 centimeters long by 10 wide. The male spikelet is somewhat oval in shape and the female is lance-shaped with a long awn which may be a few centimeters in length. The male and female flowers are on different branches of the panicle. Pollen is carried to other plants on the wind. The plant can grow by cloning
and sometimes forms mats of cloned stems.
This plant is limited to a single site on the first two miles of the San Marcos River in Texas. There are 140 clumps of stems in this population. It covers about 1200 square meters. There is also an introduced population at Spring Lake at the San Marcos Springs
and a number of specimens are kept in an enclosure on the Texas State University
campus. The natural habitat of the grass is the clear water of the San Marcos River, which is fed by springs
originating in the Edwards Aquifer
. The grass occurs in a relatively narrow range of water conditions, including temperature, pH
, and turbidity
, flow rates, and substrate types.
This plant was once locally common in the area, growing thick enough to become a nuisance as recently as the 1930s. It has been reduced to its rare status because the Edwards Aquifer has been drained of its water for use in agriculture and other industries, lowering the flow on San Marcos River. The rare plant is threatened now by recreational activities on the river, and by nutria, an introduced
mammal. Stems are broken, bent, or submerged by floating debris, including masses of vegetation mowed upstream and sent floating.
The grass is inefficient in reproduction. It rarely accomplishes successful sexual reproduction. Pollen is released for a short time each day, typically only between 2 and 4 am. It is sometimes released a second time around 9 am. Within a few minutes the pollen loses its viability and it becomes nonfunctional within one hour. Because the pollen is carried on the wind, the inflorescence must rise above the surface of the water; the stem cannot be broken or submerged. Pollen generally moves less than one meter from its parent inflorescence, so plants must be close together to reproduce and cannot be isolated. Today the plant is rare and the population is fragmented, making it difficult for the pollen to reach a receptive flower. The male flowers of the grass do not pollinate the female flowers on the same inflorescence because they do not release pollen at the same time the female flowers are receptive. The grass can also reproduce vegetatively by producing tillers
. Tillers can break off and root to produce new stems, but these will be genetically identical to the parent plant.
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
known by the common name Texas wild rice. It is endemic to Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, where it is found only on the upper San Marcos River
San Marcos River
The San Marcos River rises from the San Marcos Springs, the location of Aquarena Springs, in San Marcos, Texas. The springs are home to several threatened or endangered species, including the Texas Blind Salamander, Fountain Darter, and Texas Wild Rice...
in Hays County
Hays County, Texas
Hays County is a county located on the Edwards Plateau in the U.S. state of Texas. In 2010, its official population had reached 157,107. It is named for John Coffee Hays, a Texas Ranger and Mexican-American War officer. The seat of the county is San Marcos....
. It is threatened by the loss and degradation of its habitat. It is a federally listed endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
of the United States.
This grass, a member of the same genus as commercially sold wild rice
Wild rice
Wild rice is four species of grasses forming the genus Zizania, and the grain which can be harvested from them. The grain was historically gathered and eaten in both North America and China...
, is an aquatic plant
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...
that grows in the water with only its stem tips rising above the surface. It grows 1 to 2 meters long but the stems have been known to reach five meters in length. The ribbon-like leaves are up to a meter in length. The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
is a panicle
Panicle
A panicle is a compound raceme, a loose, much-branched indeterminate inflorescence with pedicellate flowers attached along the secondary branches; in other words, a branched cluster of flowers in which the branches are racemes....
up to 31 centimeters long by 10 wide. The male spikelet is somewhat oval in shape and the female is lance-shaped with a long awn which may be a few centimeters in length. The male and female flowers are on different branches of the panicle. Pollen is carried to other plants on the wind. The plant can grow by cloning
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...
and sometimes forms mats of cloned stems.
This plant is limited to a single site on the first two miles of the San Marcos River in Texas. There are 140 clumps of stems in this population. It covers about 1200 square meters. There is also an introduced population at Spring Lake at the San Marcos Springs
San Marcos Springs
San Marcos Springs is the second largest natural cluster of springs in Texas. The springs are located in the city of San Marcos, Texas, about 30 miles southwest of Austin and 46 miles northeast of San Antonio.-Geology:...
and a number of specimens are kept in an enclosure on the Texas State University
Texas State University–San Marcos
Texas State University–San Marcos is a doctoral-granting university located in San Marcos, Texas...
campus. The natural habitat of the grass is the clear water of the San Marcos River, which is fed by springs
Spring (hydrosphere)
A spring—also known as a rising or resurgence—is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground...
originating in the Edwards Aquifer
Edwards Aquifer
The Edwards Aquifer is one of the most prolific artesian aquifers in the world. Located on the eastern edge of Edwards Plateau in the U.S. state of Texas, it discharges about of water a year and directly serves about two million people...
. The grass occurs in a relatively narrow range of water conditions, including temperature, pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
, and turbidity
Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
, flow rates, and substrate types.
This plant was once locally common in the area, growing thick enough to become a nuisance as recently as the 1930s. It has been reduced to its rare status because the Edwards Aquifer has been drained of its water for use in agriculture and other industries, lowering the flow on San Marcos River. The rare plant is threatened now by recreational activities on the river, and by nutria, an introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
mammal. Stems are broken, bent, or submerged by floating debris, including masses of vegetation mowed upstream and sent floating.
The grass is inefficient in reproduction. It rarely accomplishes successful sexual reproduction. Pollen is released for a short time each day, typically only between 2 and 4 am. It is sometimes released a second time around 9 am. Within a few minutes the pollen loses its viability and it becomes nonfunctional within one hour. Because the pollen is carried on the wind, the inflorescence must rise above the surface of the water; the stem cannot be broken or submerged. Pollen generally moves less than one meter from its parent inflorescence, so plants must be close together to reproduce and cannot be isolated. Today the plant is rare and the population is fragmented, making it difficult for the pollen to reach a receptive flower. The male flowers of the grass do not pollinate the female flowers on the same inflorescence because they do not release pollen at the same time the female flowers are receptive. The grass can also reproduce vegetatively by producing tillers
Tiller (botany)
A tiller is a stem produced by grass plants, and refers to all shoots that grow after the initial parent shoot grows from a seed. Tillers are segmented, each segment possessing its own two-part leaf...
. Tillers can break off and root to produce new stems, but these will be genetically identical to the parent plant.