A seed plant or spermatophyte (lit.'seed plant'; from Ancient Greek σπέρματος (spérmatos) 'seed' and φυτόν (phytón) 'plant'), also known as 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.

Quick Facts Scientific classification, Extant divisions ...
Seed plants
Temporal range: Famennian–Present
Thumb
Scots pine, Pinus sylvestris, a member of the Pinophyta
Thumb
Sycamore maple, Acer pseudoplatanus, a member of the Eudicots
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Spermatophytes
Extant divisions
Synonyms
  • Phanerogamae
  • Phaenogamae
Close

The term phanerogam or phanerogamae is derived from the Greek φανερός (phanerós), meaning "visible", in contrast to 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).

Description

The extant spermatophytes form five divisions, the first four of which are classified as gymnosperms, plants that have unenclosed, "naked seeds":[1]:172

The fifth extant division is the flowering plants, also known as angiosperms or magnoliophytes, the largest and most diverse group of spermatophytes:

  • Angiosperms, the flowering plants, possess seeds enclosed in a fruit, unlike gymnosperms.

In addition to the five living taxa listed above, the fossil record contains evidence of many extinct taxa of seed plants, among those:

  • Pteridospermae, the so-called "seed ferns", 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 the angiosperms radiated.

Evolutionary history

Thumb
Drawing of Runcaria megasporangium and cupule, resembling a seed without a solid seed coat

A whole genome duplication event in the ancestor of seed plants occurred about 319 million years ago.[2] 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, 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]

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 the order Lyginopteridales.[4]

Phylogeny

Seed-bearing plants are a clade within the vascular plants (tracheophytes).[5]

Internal phylogeny

The spermatophytes were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetophytes, cycads,[5] ginkgo, and conifers. Older morphological studies believed in a close relationship between the gnetophytes and the angiosperms,[6] in particular based on vessel elements. However, molecular studies (and some more recent morphological[7][8] and fossil[9] 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:[10][11][12]

Spermatophytes
Angiosperms

(flowering plants)

Gymnosperms

Cycads

Ginkgo

Pinaceae (the pine family) Thumb

Gnetophytes Thumb

other conifers

However, the relationships between these groups should not be considered settled.[6][13]

Other classifications

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

A more modern classification ranks these groups as separate divisions (sometimes under the Superdivision Spermatophyta):[citation needed]

Unassigned extinct spermatophyte orders, some of which qualify as "seed ferns":[citation needed]

References

Wikiwand in your browser!

Seamless Wikipedia browsing. On steroids.

Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.

Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.