Creatures from the deep?
A poorly known genus of flowering plants that resemble deep-sea creatures, rather more than they do plants.
Langsdorffia is a genus of flowering plants unlike any other in appearance. Belonging to the family Balanophoraceae, four species are recognised, and these are dispersed widely: L. hypogaea, which is widespread across Central and South America; L. malagasica, which is endemic to Madagascar; L. papuana in Papua New Guinea; and the recently described L. heterotepala which is restricted to just a handful of forests in the south and southeast of Brazil.
Unlike most plants, Langsdorffia lack chlorophyll and are dependent entirely on their so-called host plants for their nutrition. All four species are root holoparasites and obtain all of their fixed carbon from a host plant. Their scaly, often brightly coloured flower heads erupt from ascending subterranean branches on the dingy forest floor, and superficially resemble deep-sea creatures, rather more than they do flowering plants. Creatures from the deep?
Life history and ecology
The Balanophoraceae comprises predominantly of tropical subterranean root parasites of shrubs, herbs, and trees that are seldom encountered or collected, and generally preserve poorly. Little is known about the life history and ecology of most species in the family.
All species of Langsdorffia are highly modified parasites comprising just a series of tubers and flowering structures and lack an ordinary stem structure and all trace of functional apical meristems (the ‘growing tips’).
Plants in the family Balanophoraceae more broadly feature a particularly complicated host‐parasite vascular interface, in which the parasitic tuber appears to engulf the host plant’s roots, the vascular tissues of which infiltrate the parasite tissue extensively. Interestingly, all Balanophoraceae appear to lack stomata (tiny openings that allow for gas exchange) entirely, which is highly unusual in the plant kingdom beyond submerged aquatics.
Little research has been carried out to examine the ‘host specificity’ (the level of preference for particular host plants) of Langsdorffia. While holoparasites are generally host-specific, L. hypogaea has been shown to parasitize over 20 host species including shrubs, trees, lianas, and even a cactus, from 16 families; however, an apparent preference for Miconia albicans (Melastomataceae) indicates at least a degree of specificity.
Reproductive biology
Little is known about the pollination biology, breeding systems, or seed dispersal of the Balanophoraceae, and Langsdorffia in particular. All species in the genus produce minute, unisexual flowers, borne in spike‐like inflorescences on the dark forest floor; however, pollination mechanisms appear to be diverse.
Species in the related genus Balanophora secrete nectar and are visited by ants, cockroaches, and moths in Japan and Lophophytum mirabile is visited by beetles in the Ecuadorian Amazon. Balanophora kuroiwai appears to have evolved as a mutualistic pollination syndrome with pyralid moths, which use the plant as a brood site for their larvae to develop, like the better‐known systems of fig–fig wasp and yucca–yucca moth. Brood‐site pollination involving Morellia flies has also been observed in the related genus Thonningia in the rainforests of West Africa.
Investigations into the reproductive biology of Langsdorffia are hampered by the rarity of the plants and a high rate of herbivory when they do appear. Indeed, virtually nothing is known about the reproductive biology of Langsdorffia with the exception of L. hypogaea.
The flowering heads of L. hypogaea comprises a fleshy, spadix‐like structure that is covered with scales with hairy margins; the male flowers are stalked, and the female flowers are sessile, and both have nectar‐producing conical structures. The flowers are brightly coloured and sweetly scented when they are in bloom, and attractive to a diversity of insects including ants and beetles.
Conservation
The conservation of holoparasitic flowering plants are impeded significantly by the complete dependency on their host plants. None of the four species of Langsdorffia exist in cultivation. This is concerning because all species occur in habitats under threat, and at least one species, L. heteropetala, may be classified as Critically Endangered in the future, because it has such a limited distribution.
Future work should focus on refining our understanding of their host specificity with a view to propagating them, and introducing them into botanic gardens’ conservation collections, safeguarding the future of these extraordinary plants.
Dr Chris J. Thorogood
Deputy Director and Head of Science
University of Oxford Botanic Garden and Arboretum
Jean Carlos Santos
Professor (Associate) Departamento de Ecologia
Universidade Federal de Sergipe, Brazil
Edited by Samantha Ibbott
University of Oxford Botanic Garden and Arboretum
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Read the fully referenced original:
https://nph.onlinelibrary.wiley.com/doi/full/10.1002/ppp3.10102
