A pteridophyte is a
vascular plant (with
xylem and
phloem) that disperses
spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...
s. Because pteridophytes produce neither
flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanis ...
s nor
seed
A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...
s, they are sometimes referred to as "
cryptogams", meaning that their means of reproduction is hidden.
Fern
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...
s,
horsetails (often treated as ferns), and
lycophytes (
clubmosses,
spikemoss
''Selaginella'' is the sole genus of vascular plants in the family Selaginellaceae, the spikemosses or lesser clubmosses.
This family is distinguished from Lycopodiaceae (the clubmosses) by having scale-leaves bearing a ligule and by having ...
es, 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, respectively. Ferns and lycophytes share a life cycle and are often collectively treated or studied, for example by the International Association of Pteridologists and the
Pteridophyte Phylogeny Group.
Description
Pteridophytes (ferns and lycophytes) are free-sporing
vascular plants that have a
life cycle with
alternating, free-living
gametophyte
A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the ...
and
sporophyte phases that are independent at maturity. The body of the sporophyte is well differentiated into roots, stem and leaves. The root systems 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) and
land plant plesiomorphies (e.g.,
spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...
dispersal and the absence of
seed
A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...
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 era, considered the ferns as monilophytes, as follows:
*
Division Tracheophyta (tracheophytes) - vascular plants
** Subdivision
Lycopodiophyta (lycophytes) - less than 1% of extant vascular plants
**
Sub division Euphyllophytina
The euphyllophytes are a clade of plants within the tracheophytes (the vascular plants). The group may be treated as an unranked clade, a division under the name Euphyllophyta or a subdivision under the name Euphyllophytina. The euphyllophytes a ...
(euphyllophytes)
*** Infradivision
Moniliformopses
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...
(monilophytes)
*** Infradivision
Spermatophyta - seed plants, ~260,000 species
where the monilophytes comprise about 9,000 species, including
horsetails
''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds.
''Equisetum'' is a "living fossil", the only living genus of the entire subclass ...
(
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
The endodermis is the central, innermost layer of cortex in land plants. It is a cylinder of compact living cells, the radial walls of which are impregnated with hydrophobic substances (Casparian strip) to restrict apoplastic flow of water to th ...
, 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
Marsileaceae () is a small family of heterosporous aquatic and semi-aquatic ferns, though at first sight they do not physically resemble other ferns. The group is commonly known as the "pepperwort family" or as the "water-clover family" because ...
,
Salviniaceae and ''
Ceratopteris
''Ceratopteris'' is the only genus among homosporous ferns that is exclusively aquatic. It is pan-tropical and classified in the Parkerioideae subfamily of the family Pteridaceae.
Description
Erect aquatic or subaquatic ferns of moderate siz ...
''), and even a much wider range of
taxa. 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 clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
, are formally only considered as four
classes (
Psilotopsida;
Equisetopsida;
Marattiopsida
Marattiaceae is the only family of extant (living) ferns in the order Marattiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Marattiales is the only order in the subclass Marattiidae. The family has six genera and abou ...
;
Polypodiopsida), 11
orders
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
and 37
families, without assigning a higher
taxonomic rank
In biological classification, taxonomic rank is the relative level of a group of organisms (a taxon) in an ancestral or hereditary hierarchy. A common system consists of species, genus, family, order, class, phylum, kingdom, domain. While ...
.
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 and
Eupolypods II).
In 2014
Christenhusz
Dr Maarten Joost Maria Christenhusz (born 27 April 1976) is a Dutch botanist, natural historian and photographer.
Career
He was born in Enschede, the Netherlands, received his undergraduate and master's degrees from Utrecht University in Bi ...
and
Chase
Chase or CHASE may refer to:
Businesses
* Chase Bank, a national bank based in New York City, New York
* Chase Aircraft (1943–1954), a defunct American aircraft manufacturing company
* Chase Coaches, a defunct bus operator in England
* Chase C ...
, 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 sublasses, 11 orders, 21 families, approx. 212 genera, approx. 10,535 species
** Subclass
Equisetidae
Equisetidae is one of the four subclasses of Polypodiopsida (ferns), a group of vascular plants with a fossil record going back to the Devonian. They are commonly known as horsetails. They typically grow in wet areas, with whorls of needle-lik ...
Warm.
** Subclass
Ophioglossidae
Ophioglossidae is one of the four subclasses of Polypodiopsida (ferns). This subclass consists of the ferns commonly known as whisk ferns, grape ferns, adder's-tongues and moonworts. It is equivalent to the class Psilotopsida in previous treatme ...
Klinge
** Subclass
Marattiidae
Marattiaceae is the only family of extant (living) ferns in the order Marattiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Marattiales is the only order in the subclass Marattiidae. The family has six genera and about ...
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
The Pteridophyte Phylogeny Group, or PPG, is an informal international group of systematic botanists who collaborate to establish a consensus on the classification of pteridophytes (lycophytes and ferns) that reflects knowledge about plant relati ...
, 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
Equisetidae is one of the four subclasses of Polypodiopsida (ferns), a group of vascular plants with a fossil record going back to the Devonian. They are commonly known as horsetails. They typically grow in wet areas, with whorls of needle-lik ...
Warm. – horsetails; 1 extant order, family and genus (''
Equisetum
''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds.
''Equisetum'' is a "living fossil", the only living genus of the entire subclass ...
'')
***Order
Equisetales
Equisetales is an order of subclass Equisetidae with only one living family, Equisetaceae, containing the genus '' Equisetum'' (horsetails).
Classification
In the molecular phylogenetic classification of Smith et al. in 2006, Equisetales, in i ...
DC. ex Bercht. & J.Presl – 1 extant family
**Subclass
Ophioglossidae
Ophioglossidae is one of the four subclasses of Polypodiopsida (ferns). This subclass consists of the ferns commonly known as whisk ferns, grape ferns, adder's-tongues and moonworts. It is equivalent to the class Psilotopsida in previous treatme ...
Klinge – 2 extant orders
***Order
Psilotales Prant – whisk ferns; 1 extant family
***Order
Ophioglossales Link – grape ferns; 1 extant family
**Subclass
Marattiidae
Marattiaceae is the only family of extant (living) ferns in the order Marattiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Marattiales is the only order in the subclass Marattiidae. The family has six genera and about ...
Klinge – marattioid ferns; 1 extant order
***Order
Marattiales
Marattiaceae is the only family of extant (living) ferns in the order Marattiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Marattiales is the only order in the subclass Marattiidae. The family has six genera and abou ...
Link – 1 extant family
**Subclass
Polypodiidae Cronquist, Takht. & W.Zimm. – leptosporangiate ferns; 7 extant orders
***Order
Osmundales Link – 1 extant family
***Order
Hymenophyllales
The Hymenophyllaceae, the filmy ferns and bristle ferns, are a family of two to nine genera (depending on classification system) and about 650 known species of ferns, with a subcosmopolitan distribution, but generally restricted to very damp pl ...
A.B.Frank – 1 extant family
***Order
Gleicheniales
:''This article defines the Gleicheniales in a loose sense. For the restricted definition, see Gleicheniaceae.''
Gleicheniales is an order of ferns in the subclass Polypodiidae (the leptosporangiate ferns). The Gleicheniales have records potenti ...
Schimp – 3 extant families
***Order
Schizaeales
Schizaeales is an order of ferns (class Polypodiopsida).
Description
While the three clades of Schizaeales are all well-distinguished from one another by numerous morphological characters, members of the order all have dimorphic fertile and ...
Schimp. – 3 extant families
***Order
Salviniales
The order Salviniales (formerly known as the Hydropteridales and including the former Marsileales) is an order of ferns in the class Polypodiopsida.
Description
Salviniales are all aquatic and differ from all other ferns in being heterosporous ...
Link – 2 extant families
***Order
Cyatheales
The order Cyatheales, which includes most tree ferns, is a taxonomic order of the fern class, Polypodiopsida. No clear morphological features characterize all of the Cyatheales, but DNA sequence data indicate the order is monophyletic. Some ...
A.B.Frank – 8 extant families
***Order
Polypodiales Link – 26 extant families
In addition to these living groups, several groups of pteridophytes are now
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed 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 preserved ...
s. These groups include the
Rhyniopsida
The rhyniophytes are a group of extinct early vascular plants that are considered to be similar to the genus ''Rhynia'', found in the Early Devonian (around ). Sources vary in the name and rank used for this group, some treating it as the class ...
,
Zosterophyllopsida
The zosterophylls are a group of extinct land plants that first appeared in the Silurian period. The taxon was first established by Banks in 1968 as the subdivision Zosterophyllophytina; they have since also been treated as the division Zosteroph ...
,
Trimerophytopsida, the
Lepidodendrales and the
Progymnospermopsida
The progymnosperms are an extinct group of woody, spore-bearing plants that is presumed to have evolved from the trimerophytes, and eventually gave rise to the gymnosperms, ancestral to acrogymnosperms and angiosperms (flowering plants). They h ...
.
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
In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...
grade.
Lifecycle
Just as with
bryophytes and
spermatophyte
A spermatophyte (; ), also known as phanerogam (taxon Phanerogamae) or phaenogam (taxon Phaenogamae), is any plant that produces seeds, hence the alternative name seed plant. Spermatophytes are a subset of the embryophytes or land plants. They inc ...
s (seed plants), the life cycle of pteridophytes involves
alternation of generations
Alternation of generations (also known as metagenesis or heterogenesis) is the predominant type of life cycle in plants and algae. It consists of a multicellular haploid sexual phase, the gametophyte, which has a single set of chromosomes alt ...
. This means that a
diploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectiv ...
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 is the male reproductive 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 with a tail known as a flagellum, ...
) or female (producing
archegonia
An archegonium (pl: archegonia), from the ancient Greek ''ἀρχή'' ("beginning") and ''γόνος'' ("offspring"), is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female ga ...
and hence
egg cell
The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete i ...
s).
*
Monoicous: each individual gametophyte produces both antheridia and archegonia and can function both as a male and as a female.
*:
Protandrous
Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...
: 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
Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy.
Monoecy is ...
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 of the sexes.
See also
*
Embryophyte
The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as sis ...
*
Fern ally
*
Plant sexuality
References
Bibliography
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External links
British Pteridological SocietyAnnual Review of Pteridological Research *
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Pteridophytes Test Questions for Papers And Quizzes [Important
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Cryptogams
Plants
Paraphyletic groups