Pteridophyte
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A pteridophyte is a
vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...
(with
xylem Xylem is one of the two types of transport tissue (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...
and phloem) that reproduces by means of
spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...
s. Because pteridophytes produce neither
flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
s nor
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s, they are sometimes referred to as " cryptogams", meaning that their means of reproduction is hidden. They are also the ancestors of the plants we see today.
Fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...
s, horsetails (often treated as ferns), and lycophytes ( clubmosses, spikemosses, and quillworts) are all pteridophytes. However, they do not form a monophyletic group because ferns (and horsetails) are more closely related to seed plants than to lycophytes. "Pteridophyta" is thus no longer a widely accepted taxon, but the term ''pteridophyte'' remains in common parlance, as do ''pteridology'' and ''pteridologist'' as a science and its practitioner, for example by the International Association of Pteridologists and the Pteridophyte Phylogeny Group.


Etymology

The name ''Pteridophyte'' is a
Neo-Latin Neo-LatinSidwell, Keith ''Classical Latin-Medieval Latin-Neo Latin'' in ; others, throughout. (also known as New Latin and Modern Latin) is the style of written Latin used in original literary, scholarly, and scientific works, first in Italy d ...
compound word created by English speakers around 1880. It is formed from the prefix ''pterido-'' meaning fern, a Latin borrowing of the Greek word ''pterís'' which derives from ''pterón'' meaning feather. The suffix, ''-phyte'', is a suffix meaning plant from the ancient Greek word phyton (φυτόν).


Description

Pteridophytes (ferns and lycophytes) are free-sporing
vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...
s that have a life cycle with alternating, free-living gametophyte and
sporophyte A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spo ...
phases that are independent at maturity. The body of the sporophyte is well differentiated into roots, stem and leaves. The root system is always adventitious. The stem is either underground or aerial. The leaves may be microphylls or megaphylls. Their other common characteristics include vascular plant apomorphies (e.g.,
vascular tissue Vascular tissue is a complex transporting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. T ...
) and land plant plesiomorphies (e.g.,
spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...
dispersal and the absence of
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s).


Taxonomy


Phylogeny

Of the pteridophytes, ferns account for nearly 90% of the extant diversity. Smith et al. (2006), the first higher-level pteridophyte classification published in the
molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
era, considered the ferns as monilophytes, as follows: * Division
Tracheophyta Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...
(tracheophytes) - vascular plants ** Subdivision Lycopodiophyta (lycophytes) - less than 1% of extant vascular plants ** Sub division Euphyllophytina (euphyllophytes) *** Infradivision Moniliformopses (monilophytes) *** Infradivision Spermatophyta - seed plants, ~260,000 species where the monilophytes comprise about 9,000 species, including horsetails ( Equisetaceae), whisk ferns (Psilotaceae), and all eusporangiate and all leptosporangiate ferns. Historically both lycophytes and monilophytes were grouped together as pteridophytes (ferns and fern allies) on the basis of being spore-bearing ("seed-free"). In Smith's molecular phylogenetic study the ferns are characterised by lateral root origin in the endodermis, usually mesarch protoxylem in shoots, a pseudoendospore, plasmodial tapetum, and sperm cells with 30-1000 flagella. The term "moniliform" as in Moniliformopses and monilophytes means "bead-shaped" and was introduced by Kenrick and Crane (1997) as a scientific replacement for "fern" (including Equisetaceae) and became established by Pryer et al. (2004). Christenhusz and Chase (2014) in their review of classification schemes provide a critique of this usage, which they discouraged as irrational. In fact the alternative name Filicopsida was already in use. By comparison "lycopod" or lycophyte (club moss) means wolf-plant. The term " fern ally" included under Pteridophyta generally refers to vascular spore-bearing plants that are not ferns, including lycopods, horsetails, whisk ferns and water ferns ( Marsileaceae, Salviniaceae and '' Ceratopteris''). This is not a natural grouping but rather a convenient term for non-fern, and is also discouraged, as is eusporangiate for non-leptosporangiate ferns. However both Infradivision and Moniliformopses are also invalid names under the International Code of Botanical Nomenclature. Ferns, despite forming a
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
, are formally only considered as four classes ( Psilotopsida; Equisetopsida; Marattiopsida; Polypodiopsida), 11 orders and 37 families, without assigning a higher
taxonomic rank In biology, taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of or ...
. Furthermore, within the Polypodiopsida, the largest grouping, a number of informal clades were recognised, including leptosporangiates, core leptosporangiates, polypods (Polypodiales), and eupolypods (including
Eupolypods I Polypodiineae is a suborder of ferns in the order Polypodiales. It is equivalent to the clade eupolypods I in earlier systems, and to the very broadly defined family Polypodiaceae in the classification of Christenhusz & Chase (2014). It probably ...
and Eupolypods II). In 2014 Christenhusz and Chase, summarising the known knowledge at that time, treated this group as two separate unrelated taxa in a consensus classification; * Lycopodiophyta (lycopods) 1 subclass, 3 orders, each with one family, 5 genera, approx. 1,300 species * Polypodiophyta (ferns) 4 subclasses, 11 orders, 21 families, approx. 212 genera, approx. 10,535 species ** Subclass Equisetidae Warm. ** Subclass Ophioglossidae Klinge ** Subclass Marattiidae Klinge ** Subclass Polypodiidae Cronquist, Takht. & Zimmerm. These subclasses correspond to Smith's four classes, with Ophioglossidae corresponding to Psilotopsida. The two major groups previously included in Pteridophyta are phylogenetically related as follows:


Subdivision

Pteridophytes consist of two separate but related classes, whose nomenclature has varied. The system put forward by the Pteridophyte Phylogeny Group in 2016, PPG I, is: * Class Lycopodiopsida Bartl. – lycophytes: clubmosses, quillworts and spikemosses; 3 extant orders ::*Order Lycopodiales DC. ex Bercht. & J.Presl – clubmosses; 1 extant family ::*Order Isoetales Prantl – quillworts; 1 extant family ::*Order Selaginellales Prantl – spikemosses; 1 extant family * Class Polypodiopsida Cronquist, Takht. & W.Zimm. – ferns; 11 extant orders ** Subclass Equisetidae Warm. – horsetails; 1 extant order, family and genus ('' Equisetum'') *** Order Equisetales DC. ex Bercht. & J.Presl – 1 extant family ** Subclass Ophioglossidae Klinge – 2 extant orders *** Order Psilotales Prant – whisk ferns; 1 extant family *** Order Ophioglossales Link – grape ferns; 1 extant family ** Subclass Marattiidae Klinge – marattioid ferns; 1 extant order *** Order Marattiales Link – 1 extant family ** Subclass Polypodiidae Cronquist, Takht. & W.Zimm. – leptosporangiate ferns; 7 extant orders *** Order Osmundales Link – 1 extant family *** Order Hymenophyllales A.B.Frank – 1 extant family *** Order Gleicheniales Schimp – 3 extant families *** Order Schizaeales Schimp. – 3 extant families *** Order Salviniales Link – 2 extant families *** Order Cyatheales A.B.Frank – 8 extant families *** Order
Polypodiales The Order (biology), order Polypodiales encompasses the major lineages of polypod ferns, which comprise more than 80% of today's fern species. They are found in many parts of the world including Tropics, tropical, semitropical and Temperate clima ...
Link – 26 extant families In addition to these living groups, several groups of pteridophytes are now
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
and known only from
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s. These groups include the Rhyniopsida, Zosterophyllopsida, Trimerophytopsida, the Lepidodendrales and the Progymnospermopsida. Modern studies of the land plants agree that seed plants emerged from pteridophytes more closer to ferns than lycophytes. Therefore, pteridophytes do not form a clade but constitute a
paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
grade.


Life cycle

Just as with
bryophyte Bryophytes () are a group of embryophyte, land plants (embryophytes), sometimes treated as a taxonomic Division (taxonomy), division referred to as Bryophyta ''Sensu#Common qualifiers, sensu lato'', that contains three groups of non-vascular pla ...
s and spermatophytes (seed plants), the life cycle of pteridophytes involves alternation of generations. This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus, which produces gametes). Pteridophytes differ from bryophytes in that the sporophyte is branched and generally much larger and more conspicuous, and from seed plants in that both generations are independent and free-living. The sexuality of pteridophyte gametophytes can be classified as follows: * Dioicous: each individual gametophyte is either male (producing antheridia and hence
sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...
) or female (producing archegonia and hence egg cells). * Monoicous: each individual gametophyte produces both antheridia and archegonia and can function both as a male and as a female. *: Protandrous: the antheridia mature before the archegonia (male first, then female). *: Protogynous: the archegonia mature before the antheridia (female first, then male). These terms are ''not'' the same as monoecious and dioecious, which refer to whether a seed plant's sporophyte bears both male and female gametophytes, i.e., produces both pollen and seeds, or just one.


See also

* Embryophyte * Fern ally *
Plant sexuality Plant reproductive morphology is the study of the physical form and structure (the morphology) of those parts of plants directly or indirectly concerned with sexual reproduction. Among all living organisms, flowers, which are the reproductive ...


References


Bibliography

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External links


British Pteridological Society

Annual Review of Pteridological Research
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Pteridophytes Test Questions for Papers And Quizzes [Important
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