Roscoea bhutanica
Encyclopedia
Roscoea bhutanica is a perennial herbaceous plant
native to the mountains of Bhutan
and Tibet
. Formerly regarded as part of Roscoea tibetica
, it was recognized as a separate species in 2000. Most members of the ginger family (Zingiberaceae
), to which it belongs, are tropical, but R. bhutanica, like other species of Roscoea
, grows in much colder mountainous regions.
native to mountains in Bhutan
and southern Tibet
. It has been found at altitudes of between 2,100 and 3,500 metres, in wooded valleys and forest clearings.
Like all members of the genus Roscoea, it dies back each year to a short vertical rhizome
, to which are attached the tuberous roots
. When growth begins again, "pseudostems" are produced: structures which resemble stems but are actually formed from the tightly wrapped bases (sheaths) of its leaves. R. bhutanica is one of the smaller members of the genus; plants are 8–14 cm tall, with around four to eight or more leaves, the first two to four being bladeless, the others with smooth (glabrous) blades 4–21 cm long by 1–1.6 cm wide. The leaves are clustered together at the base.
The stem (peduncle
) of the flower spike is hidden by the leaf sheaths. Bracts some 4.5–8 cm long by 1–1.6 wide enclose the flowers, which are purple and appear one at a time, just above the leaves.
Each flower has the typical structure for Roscoea
(see the diagrams in that article). There is a tube-shaped outer calyx, 5–6.5 cm long with a two-toothed apex. Next the three petal
s (the corolla) form a tube which is usually about 1 cm longer than the calyx at 5–6.5 cm and terminates in three lobes, a narrow upright central lobe, about 2.3–2.6 cm long and 1.1–1.3 cm wide, and two narrower side lobes, each 2.4–2.8 cm long by 4–6 mm wide. Inside the petals are structures formed from four sterile stamen
s (staminodes): two lateral staminodes form what appear to be narrow upright petals, 1.6–1.9 cm long; two central staminodes are fused to form a lip or labellum, about 2.5–3.2 cm by 1.6–2 cm, which is slightly bent downwards and divided into two lobes for less than half its length.
The single functional stamen has a white anther, about 6–7 mm long, above pointed spurs formed from the connective tissue between the two capsules of the anther. The style is pinkish-white with a white stigma. The ovary is about 1–1.7 cm long.
botanist. The specific epithet bhutanica refers to the main area of distribution of the species, namely Bhutan
.
As explained further below, the species was originally considered to be part of R. tibetica
.
.
Species of Roscoea divide into two clear groups, a Himalayan clade and a "Chinese" clade (which includes some species from outside China). The two clades correspond to a geographical separation, being divided by the Brahmaputra River
as it flows south at the end of the Himalayan mountain chain. It has been suggested that the genus may have originated in this area and then spread westwards along the Himalayas and eastwards into the mountains of China and its southern neighbours.
R. tibetica
was formerly thought to be unique in occurring on both sides of the Brahmaputra River. However, genetic analysis in 2000 showed that plants from the south of the Brahmaputra River, in Bhutan, were distinct from those from the other side of the river, in China. The former were placed in a new species, R. bhutanica. R. bhutanica falls into the Himalayan clade whereas R. tibetica belongs to the Chinese clade, as would be expected from their respective distributions.
The two species are superficially similar, in that they are both small and have a tight group of basal leaves. Young plants of the two species are not easily distinguished, but later it can be seen that R. tibetica retains a rosette of leaves, whereas R. bhutanica develops leaves in two opposite rows.
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
native to the mountains of Bhutan
Bhutan
Bhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...
and Tibet
Tibet
Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...
. Formerly regarded as part of Roscoea tibetica
Roscoea tibetica
Roscoea tibetica is a perennial herbaceous plant native to the mountains of China, being found in Tibet, Sichuan and Yunnan. The species formerly included plants found in Bhutan; in 2000, these were separated into a new species, Roscoea bhutanica. Most members of the ginger family , to which it...
, it was recognized as a separate species in 2000. Most members of the ginger family (Zingiberaceae
Zingiberaceae
Zingiberaceae, or the Ginger family, is a family of flowering plants consisting of aromatic perennial herbs with creeping horizontal or tuberous rhizomes, comprising ca. 52 genera and more than 1300 species, distributed throughout tropical Africa, Asia, and the Americas.Many species are important...
), to which it belongs, are tropical, but R. bhutanica, like other species of Roscoea
Roscoea
Roscoea is a genus of perennial plants of the family Zingiberaceae . Most members of the family are tropical, whereas Roscoea species are native to mountainous regions of the Himalayas, China and its southern neighbours. Roscoea flowers superficially resemble orchids, although they are not related...
, grows in much colder mountainous regions.
Description
Roscoea bhutanica is a perennial herbaceous plantHerbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
native to mountains in Bhutan
Bhutan
Bhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...
and southern Tibet
Tibet
Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...
. It has been found at altitudes of between 2,100 and 3,500 metres, in wooded valleys and forest clearings.
Like all members of the genus Roscoea, it dies back each year to a short vertical rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
, to which are attached the tuberous roots
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...
. When growth begins again, "pseudostems" are produced: structures which resemble stems but are actually formed from the tightly wrapped bases (sheaths) of its leaves. R. bhutanica is one of the smaller members of the genus; plants are 8–14 cm tall, with around four to eight or more leaves, the first two to four being bladeless, the others with smooth (glabrous) blades 4–21 cm long by 1–1.6 cm wide. The leaves are clustered together at the base.
The stem (peduncle
Peduncle (botany)
In botany, a peduncle is a stem supporting an inflorescence, or after fecundation, an infructescence.The peduncle is a stem, usually green and without leaves, though sometimes colored or supporting small leaves...
) of the flower spike is hidden by the leaf sheaths. Bracts some 4.5–8 cm long by 1–1.6 wide enclose the flowers, which are purple and appear one at a time, just above the leaves.
Each flower has the typical structure for Roscoea
Roscoea
Roscoea is a genus of perennial plants of the family Zingiberaceae . Most members of the family are tropical, whereas Roscoea species are native to mountainous regions of the Himalayas, China and its southern neighbours. Roscoea flowers superficially resemble orchids, although they are not related...
(see the diagrams in that article). There is a tube-shaped outer calyx, 5–6.5 cm long with a two-toothed apex. Next the three petal
Petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...
s (the corolla) form a tube which is usually about 1 cm longer than the calyx at 5–6.5 cm and terminates in three lobes, a narrow upright central lobe, about 2.3–2.6 cm long and 1.1–1.3 cm wide, and two narrower side lobes, each 2.4–2.8 cm long by 4–6 mm wide. Inside the petals are structures formed from four sterile stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s (staminodes): two lateral staminodes form what appear to be narrow upright petals, 1.6–1.9 cm long; two central staminodes are fused to form a lip or labellum, about 2.5–3.2 cm by 1.6–2 cm, which is slightly bent downwards and divided into two lobes for less than half its length.
The single functional stamen has a white anther, about 6–7 mm long, above pointed spurs formed from the connective tissue between the two capsules of the anther. The style is pinkish-white with a white stigma. The ovary is about 1–1.7 cm long.
Taxonomy
Roscoea bhutanica was first described scientifically in 2000 in a paper which gives the author of the binomial name as Chatchai Ngamriabsakul, a ThaiThailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
botanist. The specific epithet bhutanica refers to the main area of distribution of the species, namely Bhutan
Bhutan
Bhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...
.
As explained further below, the species was originally considered to be part of R. tibetica
Roscoea tibetica
Roscoea tibetica is a perennial herbaceous plant native to the mountains of China, being found in Tibet, Sichuan and Yunnan. The species formerly included plants found in Bhutan; in 2000, these were separated into a new species, Roscoea bhutanica. Most members of the ginger family , to which it...
.
Evolution and phylogeny
The Zingiberaceae family is mainly tropical in distribution. The unusual mountainous distribution of Roscoea may have evolved relatively recently and be a response to the uplift taking place in the region in the last 50 million years or so due to the collision of the Indian and Asian tectonic platesPlate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
.
Species of Roscoea divide into two clear groups, a Himalayan clade and a "Chinese" clade (which includes some species from outside China). The two clades correspond to a geographical separation, being divided by the Brahmaputra River
Brahmaputra River
The Brahmaputra , also called Tsangpo-Brahmaputra, is a trans-boundary river and one of the major rivers of Asia. It is the only Indian river that is attributed the masculine gender and thus referred to as a in Indo-Aryan languages and languages with Indo-Aryan influence...
as it flows south at the end of the Himalayan mountain chain. It has been suggested that the genus may have originated in this area and then spread westwards along the Himalayas and eastwards into the mountains of China and its southern neighbours.
R. tibetica
Roscoea tibetica
Roscoea tibetica is a perennial herbaceous plant native to the mountains of China, being found in Tibet, Sichuan and Yunnan. The species formerly included plants found in Bhutan; in 2000, these were separated into a new species, Roscoea bhutanica. Most members of the ginger family , to which it...
was formerly thought to be unique in occurring on both sides of the Brahmaputra River. However, genetic analysis in 2000 showed that plants from the south of the Brahmaputra River, in Bhutan, were distinct from those from the other side of the river, in China. The former were placed in a new species, R. bhutanica. R. bhutanica falls into the Himalayan clade whereas R. tibetica belongs to the Chinese clade, as would be expected from their respective distributions.
The two species are superficially similar, in that they are both small and have a tight group of basal leaves. Young plants of the two species are not easily distinguished, but later it can be seen that R. tibetica retains a rosette of leaves, whereas R. bhutanica develops leaves in two opposite rows.