Rottboellia cochinchinensis

Rottboellia cochinchinensis is an annual with prop roots supporting erect, laterally-branching culms which are usually between 30–300 cm in length, Cauline leaves arise from hispid leaf-sheaths with irritating hairs, especially on the lower sheaths. The leaf-sheaths are as wide as the blade at the collar and have a truncated, membranous ligule of 1mm in length. The leaves are usually between 15–45 cm long and 5-20mm wide, ==Etymology==

The genus Rottboellia was named in honour of the Danish botanist Christen Friis Rottbøll (1727–1797) by Carl Linnaeus the Younger in 1781 in the publication Supplementum Plantarum. The species epithet cochinchinensis traces its etymology back to the basionym Stegosia cochinchinensis, which was used by João de Loureiro to denote the specimen he described being from Cochinchina, now part of Vietnam. Clayton ==Habitat and ecology==

Rottboellia cochinchinensis uses C4 carbon fixation during photosynthesis and as such is mostly found in warm tropical climates with high sunlight, generally in the tropics and between the northern and southern 20 °C isotherms. Carbon fixation by this pathway allows plants to avoid the wasteful process of photorespiration and as such confers a competitive advantage to species such as R. cochinchinensis in high light intensity, high heat and low humidity conditions over C3 plants. The species can be found in a diverse array of habitats including grassland and marginal land, as well as being a major weed of perennial and rotation crops across the tropics. They are dispersed by floodwater, birds, small mammals and latterly by humans and vehicles. ==Distribution==

The natural distribution of R. cochinchinensis is somewhat unclear as the species seems to have been very successful at growing its range. Most sources assume the species is native to South-East Asia, as it was first described from specimens found in this area, with one georeferenced record from New South Wales. or even intentionally introduced for grazing in the Caribbean ==Taxonomy and systematics==

The taxonomic classification of Rottboellia cochinchinensis is largely still based on the work of Clayton and Renvoize in 1986, who placed the genus within the Andropogoneae tribe of the Panicoideae, which is a subfamily within the Grasses (Family: Poaceae). The tribe was defined morphologically by many characters including fragile racemes, subtended by a leaf-sheath, which bear pairs spikelets, one fertile and sessile and the other pedicelled and barren. Like many members of the tribe, the pairs of spikelets in R. cochinchinensis fall together with the internode at maturity. From this classification, the genus Rottboellia was thought to have evolved from a common ancestor with the Phacelurus and Coelorachis genera, with Rottboellia forming a sister clade to Zea. Clayton and Renvoize also recognised a subtribe Rottboelliinae which included the genera Coelorachis, Hackelochloa, Hemarthria and Elionurus, amongst others have found evolutionary relationships between the constituent genera more difficult to tease out. Phylogenetic methodologies have experienced difficulties in resolving evolutionary relationships within the tribe, and have pointed to rapid basal radiation and/or frequent hybridisation within the clade as possible causes. However, the merger of the genera Rottboellia and Coelorachis has been well supported. Skendzic et al. (2007) also has Hackelochloa, Hemarthria and Elionurus as sister genera within Rottboelliinea sensu Clayton and Renvoize (1986) ==Additional information==

Archaeological evidence of a Rottboellia cochinchinensis caryopsis from an Early Iron Age site on the Lulonga River in the Democratic Republic of Congo was found in the early 2010s, possibly suggesting the species native distribution covers the Old World Tropics. African communities have been known to use leaves and culms to produce mats. ==References==