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Tragus (genus)
Encyclopedia
Tragus, commonly called burr grass or carrot-seed grass, is a genus
in the grass family, Poaceae
. Plants are monoecious, stolon
iferous, and either annual
or perennial depending on the species. The genus is primarily native to Africa
, but has been introduced in subtropical and tropical areas around the world as weed
s of disturbed areas. The culms (stems) are ascending or low and mat forming, glabrous, and circular in cross-section. Blade
s are flat or folded and linear, ligule
s membraneous and trichomatous
. Flowers are born in narrow panicle
s; the primary branches are spirally arranged, each possessing 2-5 spikelets; each of these spikelets bears a single floret. Each floret has 3 stamens, the anthers of which are pale yellow. The caryopses
(grains) are elliptical and golden-brown.
Four species of Tragus have been introduced to North America: T. australianus, T. berteronianus, T. heptaneuron, and T. racemosus. The natural chromosome count is 2n = 20 in T. berteronianus, and 2n = 40 in T. racemosus. Tragus species utilize C4
photosynthesis
. They prevent erosion, but make for poor grazing and in larger numbers indicate overgrazing.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
in the grass family, Poaceae
Poaceae
The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...
. Plants are monoecious, 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:...
iferous, and either annual
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
or perennial depending on the species. The genus is primarily native to 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...
, but has been introduced in subtropical and tropical areas around the world as weed
Weed
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...
s of disturbed areas. The culms (stems) are ascending or low and mat forming, glabrous, and circular in cross-section. Blade
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
s are flat or folded and linear, ligule
Ligule
A ligule — is a thin outgrowth at the junction of leaf and leafstalk of many grasses and sedges or a strap-shaped corolla, such as that of a ray floret in plants in the daisy family....
s membraneous and trichomatous
Trichome
Trichomes are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.- Algal trichomes :...
. Flowers are born in narrow 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....
s; the primary branches are spirally arranged, each possessing 2-5 spikelets; each of these spikelets bears a single floret. Each floret has 3 stamens, the anthers of which are pale yellow. The caryopses
Caryopsis
In botany, a caryopsis is a type of simple dry fruit — one that is monocarpelate and indehiscent and resembles an achene, except that in a caryopsis the pericarp is fused with the thin seed coat....
(grains) are elliptical and golden-brown.
Four species of Tragus have been introduced to North America: T. australianus, T. berteronianus, T. heptaneuron, and T. racemosus. The natural chromosome count is 2n = 20 in T. berteronianus, and 2n = 40 in T. racemosus. Tragus species utilize C4
C4 carbon fixation
C4 carbon fixation is one of three biochemical mechanisms, along with and CAM photosynthesis, used in carbon fixation. It is named for the 4-carbon molecule present in the first product of carbon fixation in these plants, in contrast to the 3-carbon molecule products in plants. fixation is an...
photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. They prevent erosion, but make for poor grazing and in larger numbers indicate overgrazing.
List of species
- Tragus andicola
- Tragus australianus
- Tragus berteronianus
- Tragus heptaneuron
- Tragus koelerioides
- Tragus mongolorum
- Tragus pedunculatus
- Tragus racemosus