''Lacandonia'' is a

mycoheterotrophic Myco-heterotrophy (from Greek μύκης , "fungus", ἕτερος ', "another", "different" and τροφή ', "nutrition") is a symbiotic relationship between certain kinds of plants and fungi, in which the plant gets all or part of its food fro ...

plant that contains no chlorophyll and has the unusual characteristic of inverted positions of the male (

androecium 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 fila ...

) and female (

gynoecium Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils' ...

) floral parts, something that had not been seen in any other plants, with the exceptions of ''

Trithuria ''Trithuria'' is a genus of small aquatic herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Most of the 12 formally characterised species of ''Trithuria'' are found in Australia, with t ...

'' and on occasion the related ''

Triuris brevistylis ''Triuris'' is a genus in the family Triuridaceae. It consists of species that are small and achlorophyllous, occurring in tropical Mexico, Guatemala, and northern South America South America is a continent entirely in the Western He ...

''.

Description

''Lacandonia '' is a small mycoheterotrophic plant that lacks chlorophyll and has a

rhizomatous In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow ho ...

, mycotrophic habit. This genus exhibits racemous

inflorescence An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...

s and bract-like leaves. The flowers are

actinomorphic Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spirall ...

and are considered "inverted" from the typical flower arrangement–usually 3 (but sometimes two to four) stamens are in the center of the flower surrounded by 60 to 80 pistils. This characteristic where the position of the

and the

are inverted is unique in the known and described taxa of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s.Vázquez-Santana, S., Engleman, E. M., Martínez-Mena, A., and Márquez-Guzmán, J. (1998)
Ovule and seed development of ''Lacandonia schismatica'' (Lacandoniaceae)
''American Journal of Botany'', 85(3): 299-304.Márquez-Guzmán, J., Vázquez-Santana, S., Engleman, E. M., Martínez-Mena, A., and Martínez, E. (1993). Pollen development and fertilization in ''Lacandonia schismatica'' (Lacandoniaceae). ''

Annals of the Missouri Botanical Garden The ''Annals of the Missouri Botanical Garden'' is a long-established major peer-reviewed journal of botany, established in 1914 by the Missouri Botanical Garden, under the directorship of botanist and phycologist, George Thomas Moore, and still p ...

'', 80(4): 891-897.Davidse, G. and Martínez, E. (1990). The chromosome number of ''Lacandonia schismatica'' (Lacandoniaceae). ''Systematic Botany'', 15(4): 635-637. Flowers of ''Lacandonia '' are bisexual and self-pollinate and fertilize before the flower opens (preanthesis

cleistogamy Cleistogamy is a type of automatic self-pollination of certain plants that can propagate by using non-opening, self-pollinating flowers. Especially well known in peanuts, peas, and pansies, this behavior is most widespread in the grass family. How ...

). They are true flowers as opposed to pseudanthia as had been suggested earlier in the literature. Barbara A. Ambrose, Silvia Espinosa-Matías, Sonia Vázquez-Santana, Francisco Vergara-Silva, Esteban Martínez, Judith Márquez-Guzmán and Elena R. Alvarez-Buylla. (2006)
Comparative developmental series of the Mexican triurids support a euanthial interpretation for the unusual reproductive axes of ''Lacandonia schismatica'' (Triuridaceae)
''American Journal of Botany'', 93(1): 15-35. The three-celled pollen grains

germinate Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

within the anthers and the pollen tube grows through the receptacle to reach the

ovaries 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. T ...

. ''L. schismatica'' can be found flowering year-round when its environment is moist enough, with a particularly active flowering period in November and December. Owing to the prenathesis cleistogamy, a form of

autogamy Autogamy, or self-fertilization, refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species o ...

(self-pollination), the known population of ''L. schismatica'' lacks genetic variability and has a high incidence of

homozygosity Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. ...

.Coello, G., Escalante, A., and Soberon, J. (1993). Lack of genetic variation in ''Lacandonia schismatica'' in its only known locality. ''Annals of the Missouri Botanical Garden'', 80(4): 898-901. The haploid chromosome number of this species is n = 9.

Taxonomy and botanical history

''Lacandonia'' is a genus of

plants in the

Triuridaceae Triuridaceae are a family of tropical and subtropical flowering plants, including nine genera with a total of approximately 55 known species. All members lack chlorophyll and are mycoheterotrophic (obtain food by digesting intracellular fungi, o ...

, with very unusual inverted floral morphology. It has two known species: * ''

Lacandonia schismatica ''Lacandonia schismatica'' is a species of mycoheterotrophic plant in the Triuridaceae (although some taxonomists place the genus in a separate family; the Lacandonaceae.). It is endemic to Lacandon Jungle in the State of Chiapas in southern M ...

'' E.Martínez & Ramos 1989 - Chiapas in Mexico * '' Lacandonia brasiliana'' A.Melo & M.Alves 2012 - Paraíba in Brazil ''Lacandonia schismatica'' was first described by Martínez and Clara Hilda Ramos in 1989, who placed the species in its own family,

Lacandoniaceae ''Lacandonia'' is a mycoheterotrophic plant that contains no chlorophyll and has the unusual characteristic of inverted positions of the male (androecium) and female (gynoecium) floral parts, something that had not been seen in any other plants, ...

, which itself was placed in the Triuridales.Martínez, E. and Ramos, C. H. (1989). Lacandoniaceae (Triuridales): Una neuva familia de Mexico. ''Annals of the Missouri Botanical Garden'', 76(1): 128-135. In 1991, Traudel Rübsamen-Weustenfeld suggested that ''L. schismatica'' be included in the family

within the genus '' Sciaphila'', '' Peltophyllum'', or its own genus. Another study in 1998 presented data that supports the separation of ''L. schismatica'' into its own family. The

APG II system The APG II system (Angiosperm Phylogeny Group II system) of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Gr ...

transferred the genus to the

and placed that family in the Pandanales.The Angiosperm Phylogeny Group. (2003). An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. ''Botanical Journal of the Linnean Society'', 141(4): 399-436. The group was long considered monotypic until the discovery of a second species, ''Lacandonia brasiliana'', in Guaribas Biological Reserve in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

in 2012.

Evolution

The difficulty expressed in placing the species in the proper family is due to the unique floral morphology. How this inverted position of the

and

evolved is unknown, but some studies have posed hypotheses. Davidse and Martínez suggested that ''L. schismatica'' could be one of

Richard Goldschmidt Richard Benedict Goldschmidt (April 12, 1878 – April 24, 1958) was a German-born American geneticist. He is considered the first to attempt to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, gen ...

's " hopeful monsters", meaning that the inverted floral morphology could have arisen from a macromutation in the genes that control floral development. It is also possible that chromosomal repatterning, also known as chromosomal rearrangement, was the origin of this species. Since the original description and early work on this species in the 1990s, other field work has revealed some instances of ''L. schismatica'' flowers that were unisexual. The closely related species ''

'' was discovered to be mostly dioecious but a few individuals were located that had bisexual flowers with the flower arrangement inverted, just like that of the normal ''L. schismatica'' flowers. This discovery led the authors of the study to conclude that the inverted floral morphology evolved before ''L. schismatica'' and ''T. brevistylis'' diverged. Isolated populations during the

Quaternary Period The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

(around five million years ago) when temperatures in the Lacandon lowland rainforest were six to eight °C (10.8 to 14.4 °F) cooler than today. This hypothesis is supported by the geographic distribution where ''L. schismatica'' is restricted to the warmer lowlands and ''T. brevistylis'' has a distribution in the cooler highlands.

References

{{Taxonbar, from=Q18200199 Pandanales genera Parasitic plants Triuridaceae