34-439: Gnetaceae Gnetum Welwitschiaceae Welwitschia Ephedraceae Ephedra Gnetophyta ( / n ɛ ˈ t ɒ f ɪ t ə , ˈ n ɛ t oʊ f aɪ t ə / ) is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales ), grouped within the gymnosperms (which also includes conifers , cycads , and ginkgos ), that consists of some 70 species across
68-406: A clade of gymnosperms , with the gnetophytes in or near the conifers. For example, one common proposed set of relationships is known as the gne-pine hypothesis and looks like: (flowering plants) [REDACTED] Cycads [REDACTED] Ginkgo [REDACTED] Pinaceae (the pine family) [REDACTED] Gnetophytes [REDACTED] other conifers [REDACTED] However,
102-495: A phanerogam (taxon Phanerogamae ) or a phaenogam (taxon Phaenogamae ), is any plant that produces seeds . It is a category of embryophyte (i.e. land plant) that includes most of the familiar land plants, including the flowering plants and the gymnosperms , but not ferns , mosses , or algae . The term phanerogam or phanerogamae is derived from the Greek φανερός ( phanerós ), meaning "visible", in contrast to
136-414: A "bizarre and enigmatic" trio because the gnetophytes' specialization to their respective environments is so complete that they hardly resemble each other at all. Gnetum species are mostly woody vines in tropical forests, though the best-known member of this group, Gnetum gnemon , is a tree native to western Malesia . The one remaining species of Welwitschia , Welwitschia mirabilis , native only to
170-646: A fleshy aril. angiosperms (flowering plants) cycads Ginkgo Pinaceae (the pine family) gnetophytes (other conifers) Some partitions of the genetic data suggest that the gnetophytes are sister to all of the other extant seed plant groups. However, there is no morphological evidence nor examples from the fossil record to support the gnetophyte-sister hypotheses. gnetophytes angiosperms (flowering plants) cycads Ginkgo conifers Knowledge of gnetophyte history through fossil discovery has increased greatly since
204-425: A single order (Gnetales), while other classifications say they should be distributed among three separate orders, each containing a single family and genus. Most morphological and molecular studies confirm that the genera Gnetum and Welwitschia diverged from each other more recently than they did from Ephedra . Unlike most biological groupings, it is difficult to find many common characteristics between all of
238-558: A system to guide the pollen to the seed. Runcaria was followed shortly after by plants with a more condensed cupule, such as Spermasporites and Moresnetia . Seed-bearing plants had diversified substantially by the Famennian , the last stage of the Devonian. Examples include Elkinsia , Xenotheca , Archaeosperma , " Hydrasperma ", Aglosperma , and Warsteinia . Some of these Devonian seeds are now classified within
272-415: Is a controlled substance today in many places because of the risk of harmful or even fatal overdosing . With just three well-defined genera within an entire division, there still is understandable difficulty in establishing an unambiguous interrelationship among them; in earlier times matters were even more difficult, with Pearson in the early 20th century discussing about the class Gnetales, rather than
306-422: Is an integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the mutlilobed integument . It is suspected that the extension was involved in anemophilous (wind) pollination . Runcaria sheds new light on the sequence of character acquisition leading to the seed. Runcaria has all of the qualities of seed plants except for a solid seed coat and
340-481: Is the flowering plants , also known as angiosperms or magnoliophytes, the largest and most diverse group of spermatophytes: In addition to the five living taxa listed above, the fossil record contains evidence of many extinct taxa of seed plants, among those: By the Triassic period, seed ferns had declined in ecological importance, and representatives of modern gymnosperm groups were abundant and dominant through
374-531: The Erdtmanithecales . Recent research by Lee, Cibrian-Jaramillo, et al. (2011) suggests that the Gnetophyta are a sister group to the rest of the gymnosperms, contradicting the anthophyte hypothesis, which held that gnetophytes were sister to the flowering plants. In the gnetifer hypothesis, the gnetophytes are sister to the conifers , and the gymnosperms are a monophyletic group, sister to
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#1732773062018408-590: The seeds being roasted, and the foliage used as a leaf vegetable . The plant is harvested and yields a useful fiber. There is no sense of danger in consuming the fruit or the seeds. There is also a study done on the plant to see if it has any medicinal properties, finding some anti-coagulation effects due to its stilbenoid content. The family Gnetaceae is well known as a rich source of plant-derived stilbenoids as well as Cyperaceae , Dipterocarpaceae , Fabaceae , and Vitaceae . Some species of Gnetum are in danger of dying out. The habitats are being removed with
442-765: The 1980s. Although some fossils that have been proposed to be gnetophytes have been found as far back as the Permian , their affinities to the group are equivocal. The oldest fossils that are definitely assignable to the group date to the Late Jurassic. Overall, the fossil record of the group is richest during the Early Cretaceous , exhibiting a substantial decline during the Late Cretaceous. Ephedraceae Gnetaceae Welwitschiaceae Incertae sedis : Possible gnetophytes (not confirmed as members of
476-1573: The absence of multiple chloroplast genes essential for photosynthesis , a trait they seem to share with the other living members of Gnetophyta, Ephedra and Welwitschia , as well as conifers . There are over 50 different species of Gnetum . subsection Araeognemones subsection Micrognemones section Gnetum subsection Gnemonoides subsection Stipitati subsection Sessiles G. buchholzianum Engler G. africanum (de Loureiro) Welwitsch G. costatum Schum. G. gnemon von Linné G. raya Markgraf G. gnemonoides Brongniart G. leyboldii Tulasne G. nodiflorum Brongniart G. schwackeanum Taubert & Schenck ex Taubert & Markgraf G. paniculatum Spruce ex Bentham G. camporum (Markgraf) Stevenson & Zanoni G. urens (Aublet) Blume G. microcarpum Blume G. diminutum Markgraf G. klossii Merrill ex Markgraf G. parvifolium (Warburg) Cheng G. luofuense Cheng G. indicum (de Loureiro) Merrill G. hainanense Cheng ex Fu, Yu & Gilbert G. montanum Markgraf G. macrostachyum Hooker G. latifolium Blume G. edule (Willdenow) Blume G. neglectum Blume G. leptostachyum Blume G. ula Brongniart G. tenuifolium Ridley G. cuspidatum Blume There are around 50 different species of Gnetum . The Catalogue of Life lists 44 species. Many Gnetum species are edible, with
510-475: The angiosperms.The gnetifer hypothesis first emerged formally in the mid-twentieth century, when vessel elements in the gnetophytes were interpreted as being derived from tracheids with circular bordered pits, as in conifers. It however only gained strong support with the emergence of molecular data in the late 1990s. Although the most salient morphological evidence still largely supports the anthophyte hypothesis, some more obscure morphological commonalities between
544-498: The divergence between Gnetales and Pinaceae at around 241 millions of years ago, in the early Triassic while a 2021 study placed it earlier, in the Carboniferous . However, the morphological evidence remains difficult to reconcile with the gnepine hypothesis. If the gnetophytes are nested within conifers, they must have lost several shared derived characters of the conifers (or these characters must have evolved in parallel in
578-466: The dry deserts of Namibia and Angola , is a ground-hugging species with only two large strap-like leaves that grow continuously from the base throughout the plant's life. Ephedra species, known as "jointfirs" in the United States, have long slender branches which bear tiny scale-like leaves at their nodes. Infusions from these plants have been traditionally used as a stimulant , but ephedrine
612-547: The early twentieth century, the anthophyte hypothesis was the prevailing explanation for seed plant evolution, based on shared morphological characters between the gnetophytes and angiosperms. In this hypothesis, the gnetophytes, along with the extinct order Bennettitales, are sister to the angiosperms, forming the "anthophytes". Some morphological characters that were suggested to unite the anthophytes include vessels in wood, net-veined leaves (in Gnetum only), lignin chemistry,
646-552: The end of the Cretaceous , when the angiosperms radiated. A whole genome duplication event in the ancestor of seed plants occurred about 319 million years ago . This gave rise to a series of evolutionary changes that resulted in the origin of modern seed plants. A middle Devonian (385-million-year-old) precursor to seed plants from Belgium has been identified predating the earliest seed plants by about 20 million years. Runcaria , small and radially symmetrical,
680-542: The formation of phylogenetic hypotheses. Molecular phylogenies of extant gymnosperms have conflicted with morphological characters with regard to whether the gymnosperms as a whole (including gnetophytes) comprise a monophyletic group or a paraphyletic one that gave rise to angiosperms. At issue is whether the Gnetophyta are the sister group of angiosperms, or whether they are sister to, or nested within, other extant gymnosperms. Numerous fossil gymnosperm clades once existed that are morphologically at least as distinctive as
714-431: The four living gymnosperm groups, such as Bennettitales, Caytonia and the glossopterids . When these gymnosperm fossils are considered, the question of gnetophyte relationships to other seed plants becomes even more complicated. Several hypotheses, illustrated below, have been presented to explain seed plant evolution. Some morphological studies have supported a close relationship between Gnetophyta, Bennettitales and
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#1732773062018748-451: The gnetophytes and conifers lend support to the gnetifer hypothesis.These shared traits include: tracheids with scalariform pits with tori interspersed with annular thickenings, absence of scalariform pitting in primary xylem , scale-like and strap-shaped leaves of Ephedra and Welwitschia ; and reduced sporophylls . angiosperms (flowering plants) cycads Ginkgo conifers gnetophytes From
782-595: The group) Other Sources: Gnetaceae Gnetum is a genus of gymnosperms , the sole genus in the family Gnetaceae within the Gnetophyta . They are tropical evergreen trees , shrubs and lianas . Unlike other gymnosperms, they possess vessel elements in the xylem . Some species have been proposed to have been the first plants to be insect- pollinated as their fossils occur in association with extinct pollinating scorpionflies . Molecular phylogenies based on nuclear and plastid sequences from most of
816-515: The layering of cells in the apical meristem , pollen and megaspore features (including thin megaspore wall), short cambial initials, and lignin syringal groups. However, most genetic studies, as well as more recent morphological analyses, have rejected the anthophyte hypothesis. Several of these studies have suggested that the gnetophytes and angiosperms have independently derived characters, including flower-like reproductive structures and tracheid vessel elements, that appear shared but are actually
850-422: The members of the gnetophytes. The two common characteristics most commonly used are the presence of enveloping bracts around both the ovules and microsporangia as well as a micropylar projection of the outer membrane of the ovule that produces a pollination droplet, though these are highly specific compared to the similarities between most other plant divisions. L. M. Bowe refers to the gnetophyte genera as
884-540: The order Lyginopteridales . Seed-bearing plants are a clade within the vascular plants (tracheophytes). The spermatophytes were traditionally divided into angiosperms , or flowering plants, and gymnosperms , which includes the gnetophytes, cycads, ginkgo, and conifers. Older morphological studies believed in a close relationship between the gnetophytes and the angiosperms, in particular based on vessel elements . However, molecular studies (and some more recent morphological and fossil papers) have generally shown
918-445: The order. G.H.M. Lawrence referred to them as an order, but remarked that the three families were distinct enough to deserve recognition as separate orders. Foster & Gifford accepted this principle, and placed the three orders together in a common class for convenience, which they called Gnetopsida. In general the evolutionary relationships among the seed plants still are unresolved, and the Gnetophyta have played an important role in
952-509: The other two conifer lineages): narrowly triangular leaves (gnetophytes have diverse leaf shapes), resin canals, a tiered proembryo , and flat woody ovuliferous cone scales. These kinds of major morphological changes are not without precedent in the Pinales , however: the Taxaceae , for example, have lost the classical cone of the conifers in favor of a single-terminal ovule, surrounded by
986-504: The plant, similar to those found in flowering plants . Because of this, gnetophytes were once thought to be the closest gymnosperm relatives to flowering plants, but more recent molecular studies have brought this hypothesis into question, with many recent phylogenies finding them to be nested within the conifers. Though it is clear they are all related, the exact evolutionary inter-relationships between gnetophytes are unclear. Some classifications hold that all three genera should be placed in
1020-649: The result of parallel evolution. Ginkgo cycads conifers angiosperms (flowering plants) gnetophytes The gnepine hypothesis is a modification of the gnetifer hypothesis, and suggests that the gnetophytes belong within the conifers as a sister group to the Pinaceae . According to this hypothesis, the conifers as currently defined are not a monophyletic group, in contrast with molecular findings that support its monophyly. All existing evidence for this hypothesis comes from molecular studies since 1999. A 2018 phylogenomic study estimated
1054-679: The species indicate hybridization among some of the Southeast Asian species. Fossil-calibrated molecular-clocks suggest that the Gnetum lineages now found in Africa , South America and Southeast Asia are the result of ancient long-distance dispersal across seawater. Their leaves are rich in phytochemicals such as flavonoids and stilbenes. Of the species studied so far, Gnetum have photosynthetic and transpiration capacities which are considerably lower than those of other seed plants, due to
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1088-484: The term "cryptogam" or " cryptogamae " (from Ancient Greek κρυπτός (kruptós) 'hidden'), together with the suffix γαμέω ( gaméō ), meaning "to marry". These terms distinguish those plants with hidden sexual organs (cryptogamae) from those with visible ones (phanerogamae). The extant spermatophytes form five divisions, the first four of which are classified as gymnosperms , plants that have unenclosed, "naked seeds": The fifth extant division
1122-510: The three relict genera : Gnetum ( family Gnetaceae), Welwitschia (family Welwitschiaceae ), and Ephedra (family Ephedraceae ). The earliest unambiguous records of the group date to the Jurassic , and they achieved their highest diversity during the Early Cretaceous . The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements , a system of small tubes ( xylem ) that transport water within
1156-517: The trees being cut down to create industry. The tropical rainforest are being destroyed so many of the species are going extinct such as Gnetum oxycarpum . The rainforests are being torn down and being turned into farmland. Gnetum live in only a small part of the rainforest. Spermatophyte A seed plant or spermatophyte ( lit. ' seed plant ' ; from Ancient Greek σπέρματος ( spérmatos ) 'seed' and φυτόν (phytón) 'plant'), also known as
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