Camphorosmoideae

Camphorosmoideae
Camphorosma monspeliaca, Illustration
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Core eudicots
Order: Caryophyllales
Family: Amaranthaceae
Subfamily: Camphorosmoideae
A. J. Scott
Genera

about 20 genera, see text

The Camphorosmoideae is a species-rich subfamily of the Amaranthaceae, formerly in family Chenopodiaceae.

Description

The members of Camphorosmoideae are mostly dwarf shrubs or annuals (rarely perennial herbs) with spreading or ascending branches. The plants are more or less densely covered with appressed or spreading hairs. The alternate leaves are often succulent, only a few annual species have thin and flat leaves.

The inconspicuous flowers are sitting solitary or in axillary clusters of 2–3 (5) in the axil of a subtending bract. They differ from the related subfamily Salsoloideae by the absence of bracteoles. The flowers are mostly bisexual. The perianth consists of (3-) 5 membranous or scarious tepals, which are often fused for about 1/5 to 4/5 of their length. 4-5 stamens are basally fused in a hypogynous disc. They have mostly exserted anthers without appendages. The pollen grains differ from Salsoloideae by greater diameter, and higher number of smaller pores with fewer spinulae per operculum. The horizontal or more rarely vertical ovary is uniovulate, with a distinct style and 2 filiform stigmas with papillae on the entire surface.

The perianth persists end encloses the fruit. The tepals can enlarge, or develop wings, spines or long hairs, or become fleshy or woody. The seed with thin testa contains an annular or folded embryo sometimes engirdling a rudimentary central perisperm.

Photosynthesis pathway

The species of Chenolea-Clade and the great Sclerolaena-Clade are C3-plants. In Bassia/Camphorosma-Clade, the species are C4-plants, with one exception that is C3/C4-intermediate.

Distribution and evolution

The Camphorosmoideae are distributed in mainly in Australia (ca. 147 species) and in the temperate and subtropical regions of the northern hemisphere: Eurasia including North-Africa (ca. 27 species), and North-America (2 species), in South-Africa (3 species). A few species are naturalized worldwide.

They grow in different habitats as shores, salt marshes and deserts in mediterranean climate to forests, steppes and deserts in climates with summer rains, from the Sahara to the alpine zone in Central Asia. Very often they grow in dry, saline or disturbed (ruderal) sites.

The Camphorosmeae evolved in Early Miocene, probably deriving from halophytic plants growing at sea-shores in a warm-temperated climate. The species of the Chenolea-Clade are regarded as remnants of an early line of evolution. The subfamily spread from Eurasia to Australia, North America and at least two times to South Africa. The Australian lineage diversified strongly, the other lineages remained species-poor.

Systematics

Maireana sedifolia
Bassia laniflora, illustration

The taxon Camphorosmeae has been published in 1837 by Stephan Ladislaus Endlicher, as a subtribe within the Chenopodieae. Alfred Moquin-Tandon classified the taxon as a tribe in 1840. Andrew John Scott raised Camphorosmoideae to subfamily level in 1978.

Phylogenetic research by Kadereit & Freitag (2011) revealed, that the traditional classification of the taxon did not reflect the phylogenetic relationships. Most of the genera, especially Kochia and Bassia were found to be highly polyphyletic, so some of their species had to be transferred to own genera Eokochia, Spirobassia, Grubovia und Sedobassia.

The Australian species of Camphorosmeae form a relatively young group still in the process of speciation and with some hybidization between species. In phylogenetic research by Cabrera et al. (2009), the genera were not clearly separated. Probably Neobassia, Threlkeldia and Osteocarpum do not own genus rank and should be included in Sclerolaena. Likewise, Enchylaena should be included in Maireana. The species-rich genera Sclerolaena and Maireana were found to be polyphyletic, so that further investigations are needed.[1]

The subfamily Camphorosmoideae consists of only one tribe, Camphorosmeae, with 20 genera and about 179 species.

Economical importance

Some species of subfamily Camphorosmoideae are of limited economical interest. Bassia scoparia var. trichophylla is cultivated as an ornamental plant ("summer-cypress"). Bassia prostrata is increasingly important for the improvement of rangeland and phytoremediation. Bassia indica and Bassia scoparia are used as forage plants. Camphorosma monspeliaca is a traditional medicinal herb.

References

  1. 1 2 3 4 5 6 7 Jonathan Cabrera, Surrey W. L. Jacobs & Gudrun Kadereit (2009): Phylogeny of the Australian Camphorosmeae (Chenopodiaceae) and the taxonomic significance of the fruiting perianth, In: International Journal of Plant Sciences, Volume 170(4), pp. 505–521.
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