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18-596: See text Tmesipteris , the hanging fork ferns , is a genus of ferns, one of two genera in the family Psilotaceae, order Psilotales (the other being Psilotum ). Tmesipteris is restricted to certain lands in the Southern Pacific, notably Australia , New Zealand and New Caledonia . In New Zealand this hanging epiphyte is common in the warm temperate rain forests of both main islands, where it can normally be found as short spiky dark-green fronds (10–15 cm long), often with lighter bag-like sporangia at

36-503: A plant is capable of photosynthesis, but parasitizes fungi as a supplementary food supply. There are also plants, such as some orchid species, that are non-photosynthetic and obligately myco-heterotrophic for part of their life cycle , and photosynthetic and facultatively myco-heterotrophic or non-myco-heterotrophic for the rest of their life cycle. Not all non-photosynthetic or " achlorophyllous " plants are myco-heterotrophic – some non-photosynthetic plants like dodder directly parasitize

54-433: A simple vascular cylinder, homosporous and terminal eusporangia and a lack of roots. Unfortunately, no fossils of psilophytes are known to exist. A careful study of the morphology and anatomy suggests that whisk ferns are not closely related to rhyniophytes, and that the ancestral features present in living psilophytes represent a reduction from a more typical modern fern plant. Significant differences between Psilotum and

72-737: A sister group to Ophioglossales . They lack true roots and leaves are very reduced, the stems being the organs containing photosynthetic and conducting tissue. There are only two species in Psilotum and a hybrid between the two. They differ from those in Tmesipteris in having stems with many branches and a synangium with three lobes rather than two. Whisk ferns in the genus Psilotum lack true roots but are anchored by creeping rhizomes . The stems have many branches with paired enations , which look like small leaves but have no vascular tissue . Above these enations there are synangia formed by

90-420: Is a stub . You can help Misplaced Pages by expanding it . Psilotum Psilotum is a genus of fern -like vascular plants . It is one of two genera in the family Psilotaceae commonly known as whisk ferns , the other being Tmesipteris . Plants in these two genera were once thought to be descended from the earliest surviving vascular plants , but more recent phylogenies place them as basal ferns, as

108-420: Is a fern (in the broad sense that includes horsetails) and that psilophytes are sister to ophioglossoid ferns. Myco-heterotrophs Full (or obligate) myco-heterotrophy exists when a non-photosynthetic plant (a plant largely lacking in chlorophyll or otherwise lacking a functional photosystem ) gets all of its food from the fungi that it parasitizes. Partial (or facultative) myco-heterotrophy exists when

126-471: Is now known that these plants are not physiologically capable of directly breaking down organic matter and that in order to get food, non-photosynthetic plants must engage in parasitism, either through myco-heterotrophy or direct parasitism of other plants. The interface between the plant and fungal partners in this association is between the roots of the plant and the mycelium of the fungus. Myco-heterotrophy therefore closely resembles mycorrhiza (and indeed

144-593: Is the non-photosynthetic liverwort Aneura mirabilis (previously considered a species of Cryptothallus ). Partial myco-heterotrophy is common in the Gentian family , with a few genera such as Voyria being fully myco-heterotrophic; in photosynthetic orchids; and in a number of other plant groups. Some ferns and clubmosses have myco-heterotrophic gametophyte stages. The fungi that are parasitized by myco-heterotrophs are typically fungi with large energy reserves to draw on, usually mycorrhizal fungi, though there

162-556: Is thought to have evolved from mycorrhiza), except that in myco-heterotrophy, the flow of carbon is from the fungus to the plant, rather than vice versa. Most myco-heterotrophs can therefore be seen as ultimately being epiparasites , since they take energy from fungi that in turn get their energy from vascular plants . Indeed, much myco-heterotrophy takes place in the context of common mycorrhizal networks , in which plants use mycorrhizal fungi to exchange carbon and nutrients with other plants. In these systems, myco-heterotrophs play

180-582: Is unusual in that it branches dichotomously, lives underground and possesses vascular tissue. The nutrition of the gametophyte appears to be myco-heterotrophic , assisted by endophytic fungi . The genus Psilotum was first formally described in 1801 by Olof Swartz and the description was published in Journal für die Botanik (Schrader) . The name of the genus is from the Ancient Greek word psilos meaning "bare", "smooth" or "bald" referring to

198-431: The vascular tissue of other plants. The partial or full loss of photosynthesis is reflected by extreme physical and functional reductions of plastid genomes in mycoheterophic plants, an ongoing evolutionary process. In the past, non-photosynthetic plants were mistakenly thought to get food by breaking down organic matter in a manner similar to saprotrophic fungi. Such plants were therefore called " saprophytes ". It

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216-461: The U.S., P. nudum is found from Florida to Texas, and P. complanatum in Hawaii. Psilotum superficially resembles certain extinct early vascular plants, such as the rhyniophytes and the trimerophyte genus Psilophyton . The unusual features of Psilotum that suggest an affinity with early vascular plants include dichotomously branching sporophytes, aerial stems arising from horizontal rhizomes,

234-650: The bases of some of its "leaves". The plant possesses no true leaves; what appear to be leaves are flattened stems . The fronds emerge directly from the fibrous root-mats which clad the trunks of mature tree ferns such as Dicksonia and Cyathea . Tmesipteris is from the Greek language, meaning a "cut fern", referring to the truncated leaf tips. Species include: Nitta et al. 2022 and Fern Tree of life T. gracilis T. sigmatifolia T. truncata T. elongata T. horomaka T. obliqua (Long fork-fern) T. tannensis This fern -related article

252-514: The fusion of three sporangia and which produce the spores . When mature, the synangia release yellow to whitish spores which develop into a gametophyte less than 2 mm (0.08 in) long. The gametophyte lives underground as a mycoheterotroph, tapping into mycorrhizal networks to access carbon and other nutrients. When the gametophyte is mature, it is monoicous , producing both egg and sperm cells. The sperm cells swim using several flagella and when they reach an egg cell, unite with it to form

270-731: The lack of the usual plant organs, and the seeming lack of leaves. 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 south-west Europe. The highest latitudes known are in South Carolina , Cádiz province in Spain , and southern Japan for P. nudum . In

288-468: The rhyniophytes and trimerophytes are that the development of its vascular strand is exarch , while it is centrarch in rhyniophytes and trimerophytes. The sporangia of Psilotum are trilocular synangia resulting from the fusion of three adjacent sporangia, and these are borne laterally on the axes. In the rhyniophytes and trimerophytes the sporangia were single and in a terminal position on branches. Molecular evidence strongly confirms that Psilotum

306-994: The role of "mycorrhizal cheaters", taking carbon from the common network, with no known reward. A special form of mycoheterotrophic association, which appears to be a chimera between the haustorial parasitism of a parasitic plant and mycoheterotrophy, is observed in Parasitaxus usta , the only mycoheterotrophic gymnosperm . In congruence with older reports, it has been recently shown that some myco-heterotrophic orchids can be supported by saprotrophic fungi, exploiting litter- or wood-decaying fungi. In addition, several green plants (evolutionarily close to myco-heterotrophic species) have been shown to engage in partial myco-heterotrophy, that is, they are able to take carbon from mycorrhizal fungi, in addition to their photosynthetic intake. Myco-heterotrophs are found among several plant groups, mainly flowering plants . All monotropes and non-photosynthetic orchids are full myco-heterotrophs, as

324-403: The young sporophyte . A mature sporophyte may grow to a height of 30 cm (10 in) or more but has no apparent leaves. The stem has a core of thick-walled protostele in its centre surrounded by an endodermis which regulates the flow of water and nutrients. The surface of the stem is covered with stomata which allow gas exchange with the surroundings. The gametophyte of Psilotum

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