Gymnosperm
Woody seed plants with unenclosed ovules and cones.
Gymnosperms are a group of woody, perennial seed-producing plants that lack the protective outer covering surrounding seeds in flowering plants. They include conifers, cycads, ginkgos, and gnetophytes, forming the clade Gymnospermae. The name derives from Ancient Greek for 'naked seed,' referring to the unenclosed condition of their seeds, which develop on the surface of scales or leaves, often modified into cones. Gymnosperms and angiosperms together constitute the spermatophytes, or seed plants.
- field
- Botany
- known_for
- Naked seeds, dominant sporophyte phase, wind pollination in conifers
- number_of_living_species
- Over 1,000
Lore & Background
Gymnosperms have a life cycle involving alternation of generations, with a dominant diploid sporophyte phase and a reduced haploid gametophyte phase dependent on the sporophyte. They are heterosporous, producing microspores (male) and megaspores (female) in pollen cones and ovulate cones, respectively. Pollen grains are typically transferred by wind or insects, entering the ovule through a micropyle. Cycads and ginkgos have two main modes of fertilization. By far the largest group of living gymnosperms are conifers, followed by cycads, gnetophytes, and Ginkgo biloba. About 65% of gymnosperms are dioecious, but conifers are almost all monoecious. Some genera have ectomycorrhiza fungal associations, while others like Cycas have coralloid roots associated with nitrogen-fixing cyanobacteria. Gymnosperms are the most threatened of all plant groups.
Reader's Guide
Gymnosperms are significant as one of the two major lineages of seed plants, alongside angiosperms. They dominated terrestrial ecosystems during the Mesozoic era and include the largest group of living gymnosperms, conifers, which are ecologically and economically important. Their unenclosed seeds and cone structures distinguish them from flowering plants. The fossil record reveals many extinct groups, such as seed ferns and Bennettitales, indicating that angiosperms are nested within a larger gymnosperm clade. Gymnosperms occupy fewer ecological niches than angiosperms but include parasites, epiphytes, and rheophytes. The term 'gymnosperm' is often used in paleobotany for all non-angiosperm seed plants, while 'Acrogymnospermae' specifies the modern monophyletic group.
Did You Know?
- Gymnosperms include parasites (Parasitaxus), epiphytes (Zamia pseudoparasitica), and rheophytes (Retrophyllum minus).
- Conifers produce their seeds inside a protective cone called a strobilus and are almost all monoecious.
- Some mid-Mesozoic gymnosperms were pollinated by extinct scorpionflies and kalligrammatid lacewings.
- Cycads have poorly lignified wood and rely on an armor of sclerenchymatous leaf bases for structural support.
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