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Psilotum

Cladus: Eukaryota
Regnum: Plantae
Divisio: Pteridophyta
Classis: Psilotopsida
Ordo: Psilotales
Familia: Psilotaceae
Genus: Psilotum
Species: P. complanatum - P. flaccidum - P. nudum - P. triquetrum

Vernacular names
Internationalization
English: Whisk Ferns
Bahasa Indonesia: Paku Telanjang
Lietuvių: Psilotas
Українська: Псилот

Psilotum (whisk fern) is a genus of fern-like vascular plants, one of two genera in the family Psilotaceae, order Psilotales, and class Psilotopsida (the other being Tmesipteris).

Species and distribution

There are two species, Psilotum nudum and Psilotum complanatum, with a hybrid between them known, Psilotum × intermedium W. H. Wagner.

The distribution of Psilotum is tropical and subtropical, in the New World, Asia, and the Pacific, with a few isolated populations in SW Europe. The highest latitudes known are in South Carolina, Cádiz province in Spain[1], and southern Japan for P. nudum. In the U.S., one species is found from Florida to Texas, the other in Hawaii.

Relation to ferns

Psilotum superficially resembles some rhyniophytes in having apparently dichotomous branching, terminal sporangia and a lack of roots. However, careful study of the morphology and anatomy suggested that whisk ferns were not closely related to rhyniophytes.

Molecular evidence[2] strongly confirms that Psilotum is a fern. Psilophytes are sister to ophioglossoid ferns.

Gametophyte

The gametophyte of Psilotum nudum L. Beauv. (P. triquetrum Swartz) is unusual in that it branches dichotomously, lives underground and possesses vascular tissue. [3] The nutrition of the gametophyte appears to be myco-heterotrophic, assisted by endophytic fungi.[4]

References

1. ^ "Psilotum nudum". Atlas y Libro Rojo de la Flora Vascular Amenazada de España. http://www.mma.es/portal/secciones/biodiversidad/inventarios/inb/flora_vascular/pdf/1066.pdf.
2. ^ Qiu, Y-L and Palmer, J (1999) "Phylogeny of early land plants: insights from genes and genomes." Trends in Plant Science 4(1), 26-30
3. ^ Holloway, J.E. (1939) The gametophyte, embryo and young rhizome of Psilotum triquetrum Schwarz. Annals of Botany 3, 313-336
4. ^ Manton, I. (1942) A note on the cytology of Psilotum with special reference to vascular prothalli from Rangitoto Is. Annals of Botany 6 283-92

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Source: Wikipedia, Wikispecies: All text is available under the terms of the GNU Free Documentation License