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 treatments, including Smith ''et al.'' (2006). The subclass contains two orders,
Psilotales and
Ophioglossales, whose relationship was only confirmed by
molecular phylogenetic studies.
Taxonomy
Smith et al. (2006) carried out the first higher-level
pteridophyte classification published in the
molecular phylogenetic era, and considered the ferns (monilophytes), with four
classes. They placed the whisk ferns and related taxa in the class Psilotopsida, with two
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 ...
.
Mark W. Chase
Mark Wayne Chase (born 1951) is a US-born British botanist. He is noted for work in plant classification and evolution, and one of the instigators of the Angiosperm Phylogeny Group-classification for flowering plants which is partly based on DNA ...
and
James L. Reveal (2009) classified them as two separate subclasses, Psilotidae and Ophioglossidae, corresponding to those orders within a much broader grouping, the class
Equisetopsida ''sensu lato''. Christenhusz ''et al.'', 2011, included both the
Ophioglossales and
Psilotales orders in the Ophioglossidae subclass. This was continued by both
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
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(2014) and by the Pteridophyte Phylogeny Group (2016). Under the latter the subclass is one of four subclasses of
Polypodiopsida (ferns) and contains two orders, two families, 12 genera, and an estimated 129 species. The relationships between the two orders, Psilotales and Ophioglossales, has long been unclear and was only confirmed by molecular systematic studies. Psilotales have
rhizomes instead of real roots, and the roots of Ophioglossales lack both branching and
root hairs
Root hair, or absorbent hairs, are outgrowths of epidermal cells, specialized cells at the tip of a plant root. They are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, of the root. Roo ...
. The
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 ...
s of both orders are
heterotrophic and often subterranean, obtaining nutrients from
mycorrhiza instead of light.
Photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...
happens exclusively in the
sporophyte.
Plant Systematics
/ref>
The following cladogram shows a likely phylogenic relationship between subclass Ophioglossidae and the other Polypodiopsida subclasses. The first three small subclasses are sometimes informally referred to as eusporangiate ferns, in contrast to the largest subclass, Polypodiidae or leptosporangiate ferns.
The two orders, Ophioglossales and Psilotales are sister groups to each other.
References
Bibliography
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Plant subclasses
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