Photo of Cyrtorchis praetermissa Summerh. growing on a rock at the foot of the
Mulanje Massif in
MalawiShift in floral colouration from white to orange in an Cyrtorchis arcuata subsp. arcuata inflorescence due to senescence, which is characteristic for this genus[2][3]Cyrtorchis crassifolia Schltr.
The species of the genus Cyrtorchis are epiphytic or lithophytic herbs,[3] which do not have pseudobulbs.[4] The white, fragrant, star-shaped flowers are distinctly spurred.[2]
Cytology
The diploid chromosome count of Cyrtorchis arcuata is 2n = 46.[5]
Physiology
Cyrtorchis is known to utilize the
crassulacean acid metabolism,[5] which entails photosynthesis during the daytime, and gaseous exchange through open stomata during the night. This enables the plant to save water.[6]
Etymology
The generic name Cyrtorchis is composed of the Greek words "kirtos" meaning curved and "orchis" meaning testicles, which refers to orchids.[7]
The genus has been divided into the sections Cyrtorchis section Homocolleticon Summerh. and Cyrtorchis section Cyrtorchis based on differences in the shape of the
viscidium.[2] Originally the section Cyrtorchis was published as section Heterocolleticon Summerh., but it is now known as Cyrtorchis section Cyrtorchis.[9][10] The section Homocolleticon is characterized by an uniformly textured viscidium,[11] in contrast to the viscidium of section Cyrtorchis, which consists of two distinct zones.[12]
The section Homocolleticon Summerh. was elevated to a genus by Szlach. & Olszewski in 2001, but Homocolleticon (Summerh.) Szlach. & Olszewski is now a synonym of Cyrtorchis Schltr.[1][9]
Species
As of December 2022, there are 19 currently accepted species:[1]
Cyrtorchis cufodontii Chiov. is now considered to be a synonym of Ypsilopus amaniensis (Kraenzl.) D'haijère & Stévart[13]
Cyrtorchis refracta (Kraenzl.) Schltr. is now considered to be a synonym of Ancistrorhynchus refractus (Kraenzl.) Summerh.[14]
Ecology
Habitat
It grows in dense forests and rainforests, as well as in plantations. It is found growing on tree trunks and branches, which receive high levels of sunlight.[15] In addition to epiphytic growth, it can also grow as a lithophyte attached to rocks.[3]
Pollination
Several
hawk moth species of the genus Hippotion have been identified as likely pollinators of Cyrtorchis okuensis.[16]
The white flowers shift to an orange pollination[2][3] after pollination or senescence. Such post-pollination behaviour is not uncommon, and it may be explained by a reduced attractivity of flowers to pollinators,[7][17][18][19] if the flowers are no longer viable.
Young, viable Cyrtorchis arcuata inflorescence without discolouration
Older Cyrtorchis arcuata inflorescence exhibiting senescence and discolouration of older, non-viable flowers
^Foden, W. & Potter, L. 2005. Cyrtorchis arcuata (Lindl.) Schltr. subsp. arcuata. National Assessment: Red List of South African Plants version 2020.1. Accessed on 2022/12/26
^Rokni, S., Matimele, H.A., Alves, M.T., Chelene, I., Darbyshire, I., Datizua, C., De Sousa, C., Langa, C., Massingue, A.O., Mucaleque, P.A., Odorico, D., Osborne, J., Rulkens, A.J.H., Timberlake, J. & Viegas, A. 2018. Cyrtorchis glaucifolia. The IUCN Red List of Threatened Species 2018: e.T120961124A120980358.
https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T120961124A120980358.en. Accessed on 26 December 2022.