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ⓘ Spermatophyte




Spermatophyte
                                     

ⓘ Spermatophyte

The spermatophytes, also known as phanerogams or phaenogams, comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or land plants. The term phanerogams or phanerogamae is derived from the Greek φανερός, phaneros meaning "visible", in contrast to the cryptogamae from Greek κρυπτός kryptos = "hidden" together with the suffix γαμέω, gameo, "to marry". These terms distinguished those plants with hidden sexual organs from those with visible sexual organs.

                                     

1. Description

The extant spermatophytes form five divisions, the first four of which are traditionally grouped as gymnosperms, plants that have unenclosed, "naked seeds":

  • Ginkgophyta, which includes a single living species of tree in the genus Ginkgo,
  • Pinophyta, the conifers, which are cone-bearing trees and shrubs,
  • and Gnetophyta, the gnetophytes, various woody plants in the relict genera Ephedra, Gnetum, and Welwitschia.
  • Cycadophyta, the cycads, a subtropical and tropical group of plants,

The fifth extant division is the flowering plants, also known as angiosperms or magnoliophytes, the largest and most diverse group of spermatophytes. Angiosperms possess seeds enclosed in a fruit, unlike gymnosperms.

In addition to the taxa listed above, the fossil record contains evidence of many extinct taxa of seed plants. The so-called "seed ferns" Pteridospermae were one of the earliest successful groups of land plants, and forests dominated by seed ferns were prevalent in the late Paleozoic. Glossopteris was the most prominent tree genus in the ancient southern supercontinent of Gondwana during the Permian period. By the Triassic period, seed ferns had declined in ecological importance, and representatives of modern gymnosperm groups were abundant and dominant through the end of the Cretaceous, when angiosperms radiated.

                                     

2. Evolution

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 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, 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 a system to guide the pollen to the seed.

                                     

3. Relationships and nomenclature

Seed-bearing plants 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 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:

However, the relationships between these groups should not be considered settled.

Other classifications group all the seed plants in a single division, with classes for the five groups:

  • Pinopsida, the conifers, "Coniferopsida"
  • Division Spermatophyta
  • Cycadopsida, the cycads
  • Ginkgoopsida, the ginkgo
  • Gnetopsida, the gnetophytes
  • Magnoliopsida, the flowering plants, or Angiospermopsida

A more modern classification ranks these groups as separate divisions sometimes under the Superdivision Spermatophyta:

  • Ginkgophyta, the ginkgo
  • Pinophyta, the conifers
  • Gnetophyta, the gnetophytes
  • Cycadophyta, the cycads
  • Magnoliophyta, the flowering plants

An alternative phylogeny of spermatophytes based on the work by Novikov & Barabas-Krasni 2015 with plant taxon authors from Anderson, Anderson & Cleal 2007 showing the relationship of extinct clades.

Unassigned spermatophytes:

  • †Iraniales E. Taylor et al. 2008
  • †Czekanowskiales Taylor et al. 2008
  • †Hexapterospermales Doweld 2001
  • †Matatiellales Anderson & Anderson 2003
  • †Arberiopsida Doweld 2001
  • †Hlatimbiales Anderson & Anderson 2003
  • †Petriellales Taylor et al. 1994
  • †Hermanophytales E. Taylor et al. 2008
  • †Avatiaceae Anderson & Anderson 2003
  • †Dirhopalostachyaceae E. Taylor et al. 2008
  • †Vojnovskyales E. Taylor et al. 2008
  • †Alexiales Anderson & Anderson 2003
  • †Axelrodiopsida Anderson & Anderson
  • †Hamshawviales Anderson & Anderson 2003


                                     
  • notably worked to classify genera of the family Malvaceae and other spermatophytes The standard author abbreviation Rodrigo is used to indicate this person
  • plants the male cells usually swim to the eggs. As a consequence, the spermatophytes were sometimes called siphonogams. This article incorporates text from
  • at the Museum of Natural History in Stockholm in the Department of Spermatophyte Botany. From 1985 - 1986 he was also a Research Associate and BA Krukoff
  • curator. His author standard form is Wilmott and his area of interest was spermatophytes His father was an academic who taught at Homerton Training College
  • expertise lay in hepaticology, although he also studied mosses, ferns, and spermatophytes Meijer was repatriated in 1958. From May 1959, he was employed by the
  • June 2018 was a German botanist. His main areas of interest are the Spermatophytes The standard author abbreviation W.Lippert is used to indicate this
  • Dicotyledones, Families 117 163. Flora Vitiensis Nova: A New Flora of Fiji Spermatophytes Only 3. Lawai, HI: Pacific Tropical Botanical Garden. p. 408.
  • herpetologist in South Africa. Also, he contributed to the collection of spermatophyte samples for the National Herbarium which has become part of the South
  • l embryon des Phanerogames On the generation and development of the spermatophyte embryo which is remarkable for the first account of any value of
  • April 1938 in Jena, Germany is an American botanist specialized in Spermatophytes In 1962 he started working at the Smithsonian Institution as a technician
  • 1875 1956 was a botanist, whose areas of interest were mycology and spermatophytes He both preceded and succeeded James Arthur Harris 1880 1930 as Head

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