''Zizania texana'' is a rare species of

grass Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and spe ...

known by the common name Texas wild rice. It is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, where it is found only on the upper

San Marcos River The San Marcos River rises from the San Marcos Springs, the location of the Meadows Center for Water and the Environment (formerly Aquarena Springs), in San Marcos, Texas. The springs are home to several threatened or endangered species, inclu ...

Hays County Hays County is a county in the central portion of the U.S. state of Texas. It is part of the Austin-Round Rock metropolitan area. As of the 2020 census, its official population had reached 241,067. The county seat is San Marcos. Hays, alon ...

. It is threatened by the loss and degradation of its habitat. It is a federally listed

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

of the United States. This grass, a member of the same genus as commercially sold

wild rice Wild rice, also called manoomin, mnomen, psíŋ, Canada rice, Indian rice, or water oats, is any of four species of grasses that form the genus ''Zizania'', and the grain that can be harvested from them. The grain was historically and is sti ...

, is an

aquatic plant Aquatic plants, also referred to as hydrophytes, are vascular plants and Non-vascular plant, non-vascular plants that have adapted to live in aquatic ecosystem, aquatic environments (marine ecosystem, saltwater or freshwater ecosystem, freshwater ...

that grows in the water with only its stem tips rising above the surface. It grows long but the stems have been known to reach in length. The ribbon-like leaves are up to a meter (3.3 ft) in length. The

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

is a

panicle In botany, a panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a p ...

up to long by 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.''Zizania texana''.
''Grass Manual Treatment''. Retrieved August 28, 2011. The male and female flowers are on different branches of the panicle. Pollen is carried to other plants by wind.Power, P. and F. M. Oxley. August 18, 2004
Assessment of factors influencing Texas wild-rice (''Zizania texana'') sexual and asexual reproduction. 2004 Final Report.
Prepared for Edwards Aquifer Authority by the San Marcos National Fish Hatchery and Technology Center and the Lady Bird Johnson Wildflower Center. Retrieved August 28, 2011. The plant can asexually propagate by

cloning Cloning is the process of producing individual organisms with identical genomes, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction; this reproduction of an organism by itself without ...

and sometimes forms mats of cloned stems.''Zizania texana''.
''Center for Plant Conservation''. Retrieved August 28, 2011. This plant is limited to the first two miles of the San Marcos River in Texas.''Zizania texana''.
''Texas Parks & Wildlife''. Retrieved August 28, 2011. There are 140 clumps of stems in this population. It covered over in 2008 and is reportedly growing exponentially from plantings. 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 Texas State University (TXST) is a public university, public research university with its main campus in San Marcos, Texas, United States, and another campus in Round Rock, Texas, Round Rock. Since its establishment in 1899, the university has ...

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 Edwards Aquifer is one of the most prolific artesian aquifers in the world. Located on the eastern edge of the Edwards Plateau in the U.S. state of Texas, it is the source of drinking water for two million people, and is the primary water su ...

. The grass occurs in a relatively narrow range of water conditions, including temperature, pH, and

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and wa ...

, 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

has been drained of its water for use in agriculture and other industries, lowering the flow on San Marcos River. The rare plant continues to be threatened by reductions to the aquifer, and is also threatened by recreational activities on the river and by

nutria The nutria () or coypu () (''Myocastor coypus'') is a herbivore, herbivorous, semiaquatic rodent from South America. Classified for a long time as the only member of the family Myocastoridae, ''Myocastor'' has since been included within Echimy ...

, an introduced mammal. Stems are broken, bent, or submerged by floating debris, including masses of vegetation mowed upstream and sent floating.Power, P. (1996)
Direct and indirect effects of floating vegetation mats on Texas wildrice (''Zizania texana'').
''Southwestern Naturalist'' 41 (4) 462. Retrieved August 28, 2011. 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 (3.3 ft) 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.

References

{{Taxonbar, from=Q8072918 Oryzoideae Endemic flora of Texas Critically endangered flora of the United States Hays County, Texas Native grasses of Texas