Arjona Schumanniana
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''Arjona megapotamica'' is a rare species of flowering plant in the family Schoepfiaceae, native to a small area of southeastern Brazil, where it grows in cool mountain grasslands. Like other ''Arjona'' species, it is thought to be a root hemiparasite. It is a small perennial plant growing as a bunch of short twigs from a woody central knob. , ''Arjona schumanniana'' was regarded by some sources as a
synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
, by others as an independent species.


Description

''Arjona megapotamica'' is a small,
herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...
, perennial root hemiparasite. A large number of unbranched stems, 15–20(–30) cm in height, sprout from a small woody central base, called a 'xylopodium'. These stems are 1–1.5 cm in diameter, sulcate (grooved in transect profile) and glabrous (hairless). The linear leaves are alternately distributed throughout the length of the stem. The leaves are simple, sessile, coloured green, glabrous, with the leaf blade 2–3 cm long and 1–1.5 cm wide. The leaves are tipped in a point, and have 1 to 3 prominent veins. The stems are topped by a terminal inflorescence, shaped as a spiked
raceme A raceme ( or ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the s ...
. It is about 2 cm in length and densely packed with flowers. The 0.6–2 cm long, linear
bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...
s, are tipped in sharp points and villous along their margins. The flowers are sessile. They have two linear, villous bracteoles 2–3 mm in length. The perianth is tubular, hypocrateriform, yellow, 10–12 mm in length, a few trichomes dispersed internally, with five lobes. The five
stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filame ...
s have dorsifixed
anther The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...
s, and are oblong. The
ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...
is pilose, about 2 mm in length, and with pendulous ovules, a filiform, glabrous style, and a slightly 3-lobulate stigma. The ovoid fruit is ca. 3–4 mm in length with a truncated end and 10 ribs. The fruit, when eventually removed from or having fallen off the infructescence, leave an off-white scar at the base of the bract. The seeds have a cylindrical embryo.


Taxonomy

''Arjona megapotamica'' was described by Gustaf Malme in 1928, based on a specimen (the holotype) he had collected in 1901 on the , a hill overlooking the port city of Porto Alegre. In 1916 Carl Skottsberg published an article on the genus ''Arjona'', in which he noted that specimens in the Berlin Herbarium had been labelled by Karl Moritz Schumann as ''A. brasiliensis'', but that he was unable to find a formal species description for the name. In 1930,
Robert Pilger Robert Knud Friedrich Pilger (3 July 1876, in Helgoland – 1 September 1953, in Berlin)
published a description of the specimens, which he noted had been collected by
Friedrich Sellow Friedrich Sellow (var. Sello) (1789–1831) was a German botanist and natural history, naturalist. He was one of the earliest European scientific explorers of Brazil, and a major collector of Wildlife of Brazil#Plants, Brazilian flora. Friedrich ...
sometime in early 19th century, under the name ''A. schumanniana''. He rejected the
epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...
''basiliensis'', since he found that it was unclear whether the specimens had actually been collected in Brazil – Sellow had also travelled to Uruguay. , "''Arjona brasiliensis''" was not listed in the International Plant Names Index, while ''A. schumanniana'' was accepted as a separate species by
Plants of the World Online Plants of the World Online (POWO) is an online database published by the Royal Botanic Gardens, Kew. It was launched in March 2017 with the ultimate aim being "to enable users to access information on all the world's known seed-bearing plants by ...
. Both these names are regarded as synonyms of ''A. megapotamica'' by the ''Flora del Conosur''. ''A. schumanniana'' was synonymised with ''A. megapotamica'' by the Brazilian botanist
João Rodrigues de Mattos João is the Portuguese language, Portuguese equivalent of the given name John (given name), John. The diminutive is Joãozinho (disambiguation), Joãozinho and the Feminine (grammar), feminine is Joana. It is widespread in Portuguese-speaking c ...
in the Santalales volume of the ''Flora Ilustrada Catarinense'' of 1967. Although ''A. megapotamica'' had not yet been named in 1916, Skottsberg placed "''A. brasiliensis''" in his section ''Xylarjona'', based on the woody xylopodium, together with ''A. longifolia''.


Distribution

''Arjona megapotamica'' is endemic to southeastern Brazil. The species formerly occurred in the state of
Rio Grande do Sul Rio Grande do Sul (, , ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative_units_of_Brazil#List, fifth-most-populous state and the List of Brazilian st ...
on granite hills which surround the coastal city of Porto Alegre. These hills have now been extensively developed, and the species was officially declared locally extinct in Rio Grande do Sul in 2014 (Decreto Estadual RS 52.109). It also occurs in the eastern part of the Santa Catarina Plateau in Santa Catarina state according to Mattos, where it presumably may still be found.


Ecology

It is a root hemiparasite growing in cool montane grasslands. On Morro da Polícia, a 286 m high granite hill, it grew in a shrubby montane grassland. In Santa Catarina it has been collected at 1,670 m altitude in the
Serra Geral The Serra Geral (General Mountains) is a mountain range in southern Brazil, constituting the southern portion of the Serra do Mar system which runs along Brazil's southeastern coast. The Serra Geral runs parallel to the Atlantic coast in Sa ...
(
Urubici Urubici is a southern Brazilian Municipalities of Brazil, municipality located in the state of Santa Catarina (state), Santa Catarina. History Economy The economy of the region is based on agriculture and tourism. Neighboring cities Some of th ...
municipality), and 950 m in Lages municipality.


Conservation

It occurs in
Aparados da Serra National Park The Aparados da Serra National Park ( pt, Parque Nacional de Aparados da Serra) is a national park located in the Serra Geral range of Rio Grande do Sul and Santa Catarina states in the south of Brazil, between 29º07’—29º15’ S and 50º0 ...
.


References

{{taxonbar, from1=Q15603981, from2=Q15602368 Schoepfiaceae Endemic flora of Brazil Plants described in 1928 Taxa named by Gustaf Oskar Andersson Malme