Microtis (plant)

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Onion orchids
Microtis parviflora (5286199239).jpg
Microtis parviflora growing on Black Mountain in the A.C.T.
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Diurideae
Subtribe: Prasophyllinae
Genus: Microtis
R.Br., 1810
Synonyms [1]
  • GoadbyellaR.S.Rogers
  • HydrorchisD.L.Jones & M.A.Clem
  • MicrotidiumD.L.Jones & M.A.Clem

Microtis, commonly known as onion orchids or mignonette orchids is a genus of about 20 species of plants in the orchid family, Orchidaceae. Onion orchids are terrestrial herbs with a single leaf at the base of the plant. They are similar to orchids in the genus Prasophyllum in that they have an onion-like leaf. The flowers are small but often scented and attractive to their insect pollinators. They are widespread in Asia, Australia and some Pacific islands.

Contents

Microtis media subsp. media labelled close up image Microtis media (labelled).001.jpg
Microtis media subsp. media labelled close up image

Description

Orchids in the genus Microtis are terrestrial, perennial, deciduous, sympodial herbs with a few inconspicuous, fine roots and an egg-shaped to almost spherical tuber. The tuber often produces two tubers on the end of long, root-like stolons. There is a single, linear, cylindrical, onion-like leaf at the base of the plant. The leaf resembles that of the closely related genus Prasophyllum except that is entirely green (usually red at the base in Prasophyllum) and exudes clear mucilage when damaged. [2] [3] [4] [5] [6] [7]

The inflorescence is a raceme with a few to many resupinate green flowers spirally arranged on a flowering stem. Each flower has a short stalk with a small bract near its base. The broad dorsal sepal is sharp-pointed, dished on the lower side and forms a horizontal hood over the column. The lateral sepals are similar to, but much narrower than the dorsal sepal. The petals are smaller than the sepals, thin and are spread below or under the dorsal sepal. As is usual in orchids, one petal is highly modified as the central labellum. The labellum is egg-shaped to oblong and hangs or is curved against the ovary. The sexual parts of the flower are fused to the column, which is shaped like half a cylinder. Flowering time depends on the climatic region where the species is found and the fruit that follows flowering is a non-fleshy, dehiscent capsule containing up to 500 seeds. [2] [3] [5] [6] [8]

Taxonomy and naming

The genus Microtis was first formally described by Robert Brown in 1810 and the description was published in Prodromus Florae Novae Hollandiae . [9] Brown described five species at the time ( M. parviflora , M. rara , M. media , M. alba and M. pulchella ) but did not nominate a type species. [10] The name Microtis is derived from the ancient Greek words mikros (μικρός) meaning "small" and ous, genitiveōtos (οὖς, genitive ὠτός) meaning "ear", [11] referring to the small, ear-like appendages on the column. [3]

Distribution and habitat

Onion orchids are widespread in temperate areas of Australia and in sub-tropical Queensland, occurring in all states but not the Northern Territory. Microtis parviflora and M. unifolia are the most widely distributed species and also occur on both main islands of New Zealand and as far south as Stewart and possibly Auckland Islands as well as New Caledonia, and Norfolk, Lord Howe and the Kermadec Islands in the western Pacific. These two species are also found in Malaysia, Indonesia, the Philippines, Taiwan, southern Japan, the Ryukyu Islands and possibly on the Chinese mainland. They usually grow in areas that are wet in winter or in areas of high rainfall. [3]

Ecology

Disease

The leaves of onion orchids are susceptible to fungal disease and most leaves appear to have some damage. The rust Uromyces microtidis has been identified as a pathogen. [3]

Pollination

Microtis flowers are insect pollinated. For some species, the insect is a small wasp from a species of Ichneumonidae or Braconidae. Pollination of orchids by ants is rare because the mouthparts of ants usually have antibiotic secretions which damage pollen grains. However, several species of Microtis, including M. parviflora are pollinated by wingless worker ants from the genera Iridomyrmex (Family Dolichoderinae), Meranops (Family Myrmeciinae) and Rhytidoponera (Family Ponerinae), having been attracted by nectar secreted from the base of the labellum. [4] [12]

Autogamy

Autogamy has been observed in several species of onion orchid. In some cases, the pollen grains fall onto the stigma and germinate but in others, including in some populations of M. parvifolia, if the flowers have not been cross-pollinated, the stigma grows upwards until it contacts the pollinia, so that seed is always produced. [4]

Species

The taxonomy of Microtis has been confused ever since Robert Brown first described the genus. He did not include Ophrys unifolia G.Forst. (1786) [13] and Epipactis porrifolia Sw. (1800) [14] and these names were used by later authors, although now recognised as Microtis media. The small size of the flowers and their tendency to change when dried as herbarium species led to further confusion. [3]

Use in horticulture

Most Microtis are very easy to grow, and readily volunteer themselves in other pots. Onion orchids are often found in gardens around Melbourne from wind-born seed. [4]

Related Research Articles

<i>Prasophyllum</i>

Prasophyllum, commonly known as leek orchids, is a genus of about 140 species of flowering plants in the orchid family, Orchidaceae and is found in Australia and New Zealand. The Australian species are found in all states but have not been recorded in the Northern Territory. The common name arises from their having a hollow, leek- or onion-like leaf. Some species only flower after summer fires and have flowers similar to those of Xanthorrhoea which flower at the same time, suggesting that they employ the same pollinating insects. Leek orchids are similar to those in the genus Genoplesium except that the free part of the leaf is cylindrical and the labellum has a solid connection to the column. They range in size from the little laughing leek orchid at about 15 cm (6 in) to the king leek orchid which grows up to 2 m (80 in) tall.

<i>Eriochilus</i> Genus of orchids

Eriochilus, commonly known as bunny orchids, is a genus of flowering plants in the orchid family, Orchidaceae that is endemic to Australia. Orchids in this genus are distinguished from those in the similar Caladenia by having a glabrous leaf and a densely woolly labellum. Species occur in south-west Western Australia, South Australia, Queensland, New South Wales, the Australian Capital Territory, Victoria, and Tasmania. Their common name alludes to their prominent ear-like lateral sepals.

<i>Microtis media</i> Species of orchid

Microtis media, commonly known as the common mignonette orchid, is a species of herbaceous plants of the family Orchidaceae endemic to the south–west of Western Australia. It has a single tubular leaf and up to one hundred small, yellowish green flowers arranged along the flowering stem.

<i>Microtis unifolia</i> Species of orchid

Microtis unifolia, commonly known as the common onion orchid, is a species of orchid occurring from south China to Japan, Malesia, and Australasia to the Southwest Pacific. It has a single green leaf and up to one hundred small green or yellowish-green flowers. A common, widespread orchid which is easily grown in pots and is sometimes a weed in plant nurseries.

<i>Genoplesium</i> Genus of orchids

Genoplesium commonly known as midge orchids, is a genus of about 50 species of flowering plants in the orchid family, Orchidaceae and is found in Australia, New Zealand and New Caledonia. Midge orchids are terrestrial herbs with a single leaf at the base of the plant. They are similar to orchids in the genus Prasophyllum in that plants without flowers have a hollow, onion-like leaf. The flowers are small but often scented and attractive to their insect pollinators. There is disagreement about which species belong to this genus and some taxonomists suggest that most belong in the genus Corunastylis.

<i>Caleana</i> Genus of flowering plants

Caleana, commonly known as duck orchids, is a genus of flowering plants in the orchid family, Orchidaceae that is found in Australia and New Zealand. The Australian species are found in all states but have not been recorded in the Northern Territory. Duck orchids have a single leaf and one or a few, dull-coloured, inconspicuous flowers. Most species are found in Western Australia but one species occurs in eastern Australia and one occurs in eastern Australia and New Zealand. Orchids in this genus as well as the hammer orchids (Drakaea) are pollinated by male thynnid wasps.

<i>Microtis parviflora</i> Species of orchid

Microtis parviflora, commonly known as the slender onion-orchid, is a species of orchid which is native to Australia and New Zealand. It occurs in all states of Australia but is not known from the Northern Territory and may not occur in Western Australia. As with others in the genus, it has a single erect, smooth, tubular leaf and up to eighty flowers on an erect flower spike.

<i>Microtis media <span style="font-style:normal;">subsp.</span> media</i> Subspecies of orchid

Microtis media subsp. media, commonly known as the common mignonette orchid, is a species of orchid which is endemic to the south–west of Western Australia. It is a common, widespread orchid with a single smooth, tubular leaf and a flowering spike with up to one hundred small green flowers. It differs from Microtis media subsp. densiflora in the shape of its flower spike and the shape of its labellum.

Microtis media subsp. densiflora, commonly known as the dense mignonette orchid, is a species of orchid which is endemic to the south–west of Western Australia. It has a single smooth, tubular leaf and a flowering spike with up to one hundred and fifty small yellowish-green flowers. It differs from Microtis media subsp. media in the shape of its flower spike and the shape of its labellum.

Microtis quadrata, commonly known as the south coast mignonette orchid or south coast onion orchid, is a species of orchid endemic to south-west coastal areas of Western Australia. It has a single thin, hollow, onion-like leaf and up to one hundred small, pale green flowers. This onion orchid grows on low mounds in swamps, often with other species of mignonette orchids, and flowers much more prolifically after fire.

Microtis eremaea, commonly known as the slender mignonette orchid or inland onion orchid is a species of orchid endemic to the south-west of Western Australia and western South Australia. It has a single thin, hollow, onion-like leaf and up to fifty small greenish-yellow flowers. The flowers have a distinctive heart-shaped labellum and the orchid generally grows in more inland areas than most other onion orchids.

Microtis eremicola, commonly known as the desert mignonette orchid or dryland onion orchid, is a species of orchid endemic to the south-west of Western Australia. It has a single hollow, onion-like leaf and up to fifty small, dull green to greenish-yellow flowers. This onion orchid is common in soil pockets on granite outcrops in inland areas, mostly between Hyden and Balladonia.

Microtis familiaris, commonly known as the coastal mignonette orchid or coastal onion orchid is a species of orchid endemic to the south-west coastal region of Western Australia. It has a single hollow, onion-like leaf and up to twenty small, green to greenish-yellow, sweetly scented, widely spaced flowers. It often grows with large populations of other Microtis orchids but only flowers after fire.

Microtis globula, commonly known as the globular mignonette orchid or globular onion orchid is a species of orchid endemic to the south-west coastal region of Western Australia. It has a single hollow, onion-like leaf and up to thirty five small greenish-yellow, almost globe-shaped flowers. It often grows in large colonies but only flowers after hot fires the previous summer.

<i>Microtis oblonga</i> Species of orchid

Microtis oblonga, commonly known as the sweet onion orchid, is a species of orchid endemic to south-eastern Australia. It has a single hollow, onion-like leaf and up to fifty scented, bright green flowers. It is considered by some Australian authorities to be synonymous with Microtis rara.

Microtis rara, commonly known as the scented onion orchid, is a species of orchid endemic to Australia, with the exception of the Northern Territory. It has a single hollow, onion-like leaf and up to fifty small green or yellowish-green, scented flowers. It is similar to Microtis oblonga and some authorities regard the two as being one species.

Microtis graniticola, commonly known as the granite mignonette orchid or granite onion orchid is a species of orchid endemic to the south-west of Western Australia. It has a single thin, hollow, onion-like leaf and up to sixty small green to greenish-yellow flowers. It grows in soil pockets on granite outcrops, especially where the soil receives run-off during rainy weather.

<i>Microtis orbicularis</i> Species of orchid

Microtis orbicularis, commonly known as the dark mignonette orchid, is a species of orchid endemic to southern Australia. It has a single thin, more or less hollow, onion-like leaf and up to fifty small yellowish-green and red flowers. The plants grow in winter-wet areas, often in shallow water and unlike the similar M. cupularis do not turn black as they dry.

Microtis pulchella, commonly known as the beautiful mignonette orchid or beautiful onion orchid, is a species of orchid endemic to the south-west of Western Australia. It has a single hollow, onion-like leaf and up to twenty five white, thinly textured flowers with a slight perfume. It only flowers after fire and only sometimes produces short, thread-like leaves in the absence of fire.

Robert J. "Rob" Bates is an Australian botanist, plant collector, and illustrator.

References

  1. ↑ "Microtis". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew . Retrieved 9 July 2016.
  2. 1 2 Hoffman, Noel; Brown, Andrew (2011). Orchids of South-West Australia (3rd ed.). Gooseberry Hill: Noel Hoffman. pp. 333–349. ISBN   9780646562322.
  3. 1 2 3 4 5 6 Bates, Robert J. (1984). "The genus Microtis R.Br. (Orchidaceae): A taxonomic revision with notes on biology". Journal of the Adelaide Botanic Garden. 7 (1): 45–89.
  4. 1 2 3 4 Pridgeon (ed.), Alec M.; Cribb (ed.), Phillip J.; Chase (ed.), Mark W.; Rasmussen (ed.), Finn (2001). Genera Orchidacearum, Volume 2, Orchidoideae (part 1). Oxford, England: Oxford University Press. pp. 181–186. ISBN   0198507100.CS1 maint: extra text: authors list (link)
  5. 1 2 Rowe, Ross. "Genus Microtis". Royal Botanic Gardens Sydney: plantnet. Retrieved 9 July 2016.
  6. 1 2 "Microtis". Royal Botanic Gardens Victoria:Vicflora. Retrieved 9 July 2016.
  7. ↑ "Microtis". State Herbarium of South Australia:efloraSA. Retrieved 9 July 2016.
  8. ↑ "Microtis". FloraBase . Western Australian Government Department of Parks and Wildlife.
  9. ↑ "Microtis". APNI. Retrieved 9 July 2016.
  10. ↑ Brown, Robert (1810). Prodromus Florae Novae Hollandiae (Vol. 1). London. p. 320. Retrieved 9 July 2016.
  11. ↑ Backer, C.A. (1936). Verklarend woordenboek der wetenschappelijke namen van de in Nederland en Nederlandsch-Indië in het wild groeiende en in tuinen en parken gekweekte varens en hoogere planten (Edition Nicoline van der Sijs).
  12. ↑ Abrol, Dharam P. (2010). Pollination biology : biodiversity conservation and agricultural production . Dordrecht: Springer. p.  288. ISBN   9789400719415.
  13. ↑ "Ophrys unifolia". APNI. Retrieved 9 July 2016.
  14. ↑ "Epipactis porrifolia". APNI. Retrieved 9 July 2016.
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