Chromolaena

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Chromolaena
Chromolaena odorata

Chromolaena odorata

Systematics
Order : Astern-like (Asterales)
Family : Daisy family (Asteraceae)
Subfamily : Asteroideae
Tribe : Eupatorieae
Sub tribus : Praxelinae
Genre : Chromolaena
Scientific name
Chromolaena
DC.

Chromolaena is a genus of plants within the sunflower family (Asteraceae). This genus is neotropically distributedwith 165 to 176 species.

description

Habit and opposite, simple leaves in the vegetative state of Chromolaena odorata
Section of an inflorescence with flower heads of Chromolaena odorata , the several rows of bracts are clearly visible.
Achenes with pappus of Chromolaena odorata

Appearance and leaves

The Chromolaena species grow as perennial herbaceous plants or semi-shrubs to shrubs and usually reach heights of 20 to 250 centimeters. The independently upright to climbing stem axes are sparsely to densely branched. Fiber roots are always formed.

The most opposite, rarely alternate or whorled arranged on the stem axis leaves are stalked or sitting. Striking and typical of the genus Chromolaena are three main nerves extending from the base; it is seldom any different. The simple leaf blades are mostly delta to ovate or elliptical, sometimes linear. The leaf margin is almost smooth to toothed or lobed. The leaf surfaces are hairless or downy to woolly and sometimes dotted with glands.

Inflorescences, flowers and fruits

In dense to open, umbrella-clustered or thyrsen-shaped total inflorescences there are more or less zymous partial inflorescences, each containing several cup-shaped partial inflorescences; rarely is a single flower head on a long, upright inflorescence stem. The flower heads are disc-shaped. In a mostly bell-shaped to hemispherical involucre with a diameter of 2 to 7 millimeters, the 18 to more than 65 bracts overlap each other in four to more than six rows. The distinctly unequal, often not very long-lasting, parchment-like or herbaceous, egg-shaped to elongated bracts (involucral sheets ) that fall off at the latest at the time of fruiting have an enlarged herbaceous or colored upper end and three to five nerves. The flat to somewhat conical inflorescence base (receptacle) can sometimes have chaff leaves . There are no ray flowers (= ray flowers).

The usually 15 to 40 (6 to 75) tubular flowers are hermaphroditic. The colors of the petals range from white, blue, purple to lavender or, more rarely, reddish. The five petals are fused to form a cylindrical corolla tube that is three to four times longer than its diameter. The corolla tubes are hardly narrower at their base. The five crown teeth are slightly to significantly longer than wide. The corolla tubes are bare on the outside, only below the coronet teeth they have a few to many short-stalked glands and often stiff hair. The corolla lobes are about as long as they are wide. The corolla lobes are subg on the inside of Chromolaena . Chromolaena papillae and in Chromolaena subg. Osmiella bald. The anthers are blunt at their base. The anthers have large, elongated appendages that are one and a half times as long as they are wide with a smooth or notched top. The two bare stylus branches protruding above the corolla tube are not widened in the lower area, narrow-linear to linear-club-shaped, i.e. somewhat widened in the upper area, and somewhat warty to dense, long papilose .

The prismatic achenes are three to five-ribbed, usually dotted with glands and hairy hairs mainly on the ribs. The pappus consists of about 40 free, durable bristles arranged in a circle, which are only rarely widened in the lower area.

Chromosome number

The basic chromosome number is x = 10, 16.

distribution

The genus Chromolaena has a neotropical distribution. Species thrive in subtropical to tropical areas. They occur from the southeast to south-central USA via Mexico to Central America and in South America , especially Brazil. One species, Chromolaena odorata , is cultivated and is a neophyte in many areas of the world ; it is considered to be an aggressive invasive plant .

Systematics

The genus Chromolaena was established in 1836 by Augustin-Pyrame de Candolle in Prodromus Systematis Naturalis Regni Vegetabilis , Volume 5, p. 133. Type species is Chromolaena horminoides DC. The genus name Chromolaena derives from the Greek words chroma for color and laina for coat, perhaps referring to the colored bracts of some species, including the type species. Synonyms for Chromolaena DC. are: Eupatorium sect. Cylindrocephala DC. , Osmia Sch.Bip. , Heterolaena Sch.Bip. ex Benth. & Hook. f. , Eupatorium L. sect. Osmia (Sch.Bip.) Benth. ex Baker , Eupatorium L. sect. Chromolaena (DC.) Benth. ex Baker , Eupatorium L. sect. Heterolaena (Sch.Bip. Ex Benth. & Hook.f.) Baker . The last revision of the genus Chromolaena was in RM King, & H. Robinson: Studies in the Eupatorieae (Compositae). XXIX. The genus Chromolaena , In: Phytologia , Volume 20, Issue 3, 1970, pp. 196-209.

The species were formerly in the genus Eupatorium L. in the section Chromolaena DC. posed. The genus Chromolaena belongs to the subtribe praxelinae from the tribe Eupatorieae in the subfamily Asteroideae within the family Asteraceae . The Chromolaena species do not belong to the genus Eupatorium , especially because they have several (at least four) rows of bracts and usually have three main nerves on the leaf blade.

There are two subgenera: Chromolaena subg. Osmiella R.M. King & H.Robinson and Chromolaena subg. Chromolaena .

There are 165 to 176 species in the genus Chromolaena :

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Individual evidence

  1. ↑ a b c d e f g h i j k l m Guy L. Nesom: Chromolaena , p. 544 - same text online and printed work : Tribus Eupatorieae , In: Flora of North America Editorial Committee (ed.): Flora of North America North of Mexico , Volume 21 - Magnoliophyta: Asteridae (in part): Asteraceae, part 3 , Oxford University Press, New York and Oxford, 2006, ISBN 0-19-530565-5 .
  2. ↑ a b c d e f g h i Yilin Chen, Takayuki Kawahara & DJ Nicholas Hind: Tribus Eupatorieae : Chromolaena , p. 883 - online with the same text as the printed work , In: Wu Zheng-Yi, Peter H. Raven & Deyuan Hong ( Editors): Flora of China , Volume 20-21 - Asteraceae , Science Press and Missouri Botanical Garden Press, Beijing and St. Louis, November 12, 2011. ISBN 978-1-935641-07-0
  3. ↑ First publication scanned at biodiversitylibrary.org.
  4. ^ Chromolaena at Tropicos.org. Missouri Botanical Garden, St. Louis
  5. ^ Compositae of Bolivia at Kew.
  6. ↑ a b c d e f g Chromolaena in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland.
  7. ↑ Assessment of recognized names in the Global Compositae Checklist .

Web links

Commons : Chromolaena  - collection of images, videos and audio files