''Hydnora visseri'', the Visser's hydnora, is a subterranean

holoparasitic A parasitic plant is a plant that derives some or all of its nutritional requirements from another living plant. They make up about 1% of angiosperms and are found in almost every biome. All parasitic plants develop a specialized organ called the ...

plant, lacking leaves and roots, and is described from southwestern

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

and northwestern

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

and has the longest tepal lobes of all ''

Hydnora ''Hydnora'' is a group of parasitic plants described as a genus in 1775. It is native to Africa, Madagascar, and the Arabian Peninsula. Hydnora pollinates through brood-site mimicry. This is a method of pollination in which the plant emits a sme ...

'' species. The genus ''Hydnora'' is composed entirely of holoparasitic plants that attach to the root of their hosts and are restricted to Africa and southwestern Asia.

Description

''Hydnora visseri'', as a holoparasitic plant, lacks chlorophyll and depends entirely on its hosts, '' Euphorbia gregaria'' or ''E. gummifera'', for all water and nutrition. ''H. visseri'' lacks leaves and roots. The vegetative body of the plant is a brown warty rhizome that spreads laterally through the soil. The bumps on the rhizome of ''Hydnora'' spp. can differentiate into

haustoria In botany and mycology, a haustorium (plural haustoria) is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates th ...

(specialized organs for parasitizing the host plant), flower buds, or bifurcations of the rhizome. The rhizomes when broken are reddish to pink and contain high levels of tannins. The only portion of the plant that emerges from the soil surface is the large fleshy flower. The

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...

of Visser's hydnora involves a trap and release mechanism where dermestid beetles are detained for several days, then released dusted with pollen. The fruit is a large berry with thousands of small (< 1mm diameter) seeds, and is usually buried or just at the soil surface.

Taxonomy

In South African and Namibia where ''Hydnora visseri'' may be encountered, four other ''Hydnora'' species exist, ''H. abyssincia'', ''H. africana'', ''H. longicollis'' and ''H. triceps''. ''H. visseri'' can be discriminated from those taxa by its exclusive hosts ''Euphorbia gummifera'' and ''E. gregaria'', and by having the longest tepals of any ''Hydnora'' spp. in Southern Africa, 5.5–9 cm long. The family

Hydnoraceae Hydnoroideae is a subfamily of parasitic flowering plants in the order Piperales. Traditionally, and as recently as the APG III system it given family rank under the name Hydnoraceae. It is now submerged in the Aristolochiaceae. It contains two ge ...

has been submerged within the

Aristolochiaceae The Aristolochiaceae () are a family, the birthwort family, of flowering plants with seven genera and about 400 known species belonging to the order Piperales. The type genus is ''Aristolochia'' L. Description They are mostly perennial, he ...

in the Piperales, based on a modern phylogenetic study that also found that the plastome of ''H. visseri'' is highly reduced, relative to photosynthetic plants, with only 27K base pairs.

Etymology

* Genus name (

generic epithet Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

): ''Hydnora'' derives from the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

, '

truffle A truffle is the fruiting body of a subterranean ascomycete fungus, predominantly one of the many species of the genus ''Tuber''. In addition to ''Tuber'', many other genera of fungi are classified as truffles including '' Geopora'', '' Pe ...

', because of the somatic structure of this root parasite. * Species name ( specific epithet): ''H. visseri'' is named after

Stellenbosch University Stellenbosch University ( af, Universiteit Stellenbosch) is a public research university situated in Stellenbosch, a town in the Western Cape province of South Africa. Stellenbosch is the oldest university in South Africa and the oldest extant ...

professor Johann H. Visser (1931-1990) and author of the text ''South African Parasitic Flowering Plants''.

Distribution and habitat

''Hydnora visseri'' grows in the winter rainfall and transitional rainfall areas of the

Karas Region Karas may refer to: Places * Karas Region, Namibia * Karaš River, a river in Serbia and Romania (Romanian ''Caraş'') * Karas Island, an island in Sebakor Bay, West Papua, Indonesia * Karaś, Kuyavian-Pomeranian Voivodeship, a village in nor ...

of Namibia and the Northern Cape province of South Africa. It occurs in a limited distribution centred around the

Orange River The Orange River (from Afrikaans/Dutch: ''Oranjerivier'') is a river in Southern Africa. It is the longest river in South Africa. With a total length of , the Orange River Basin extends from Lesotho into South Africa and Namibia to the north ...

, and is only present where its hosts ''Euphorbia gummifera'' and ''E. gregaria'' are present. ''H. visseri'' does not occur in the Karoo, nor a Karoo-type habitat, but is present in a region which the WWF has called the Succulent-Karoo and/or Nama-Karoo biomes. ''Hydnora visseri'' is most easily located by searching in around the base of the host ''

Euphorbia ''Euphorbia'' is a very large and diverse genus of flowering plants, commonly called spurge, in the family Euphorbiaceae. "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to t ...

'' plants.

Genomics

''Hydnora visseri'' possesses one of the smallest

plastid genome Chloroplast DNA (cpDNA) is the DNA located in chloroplasts, which are photosynthetic organelles located within the cells of some eukaryotic organisms. Chloroplasts, like other types of plastid, contain a genome separate from that in the cell nuc ...

s among

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s. As compared to the

chloroplast genome Chloroplast DNA (cpDNA) is the DNA located in chloroplasts, which are photosynthetic organelles located within the cells of some eukaryotic organisms. Chloroplasts, like other types of plastid, contain a genome separate from that in the cell Cel ...

of its closest photosynthetic relatives, the

plastome Chloroplast DNA (cpDNA) is the DNA located in chloroplasts, which are photosynthetic organelles located within the cells of some eukaryotic organisms. Chloroplasts, like other types of plastid, contain a genome separate from that in the cell n ...

of ''Hydnora visseri'' shows extreme reduction in both size (27,233 bp) and gene content (24 genes appear to be functional).

Conservation

Based on the Red List of South African Plants, ''H. visseri'' is considered a taxon of '

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

' due to its widespread distribution in regions with large protected areas, such as the

ǀAi-ǀAis/Richtersveld Transfrontier Park The ǀAi-ǀAis/Richtersveld Transfrontier Park is a peace park straddling the border between South Africa and Namibia. It was formed in 2003 by combining the Namibian ''ǀAi-ǀAis Hot Springs Game Park'' and the South African ''Richtersveld Nat ...

and Tsau ǁKhaeb National Park.

References

{{Taxonbar, from=Q18032175 Aristolochiaceae Plants described in 2011