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Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or on their own as in yew, Torreya, and Ginkgo. [2] The life cycle of a gymnosperm involves alternation of generations, with a dominant diploid sporophyte phase, and a reduced haploid gametophyte phase, which is dependent on the ...
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (/ p ɪ ˈ n ɒ f ɪ t ə, ˈ p aɪ n oʊ f aɪ t ə /), also known as Coniferophyta (/ ˌ k ɒ n ɪ f ə ˈ r ɒ f ɪ t ə,-oʊ f aɪ t ə /) or Coniferae. The division contains a single extant class, Pinopsida.
The name comes from the Greek for "naked seed"; the egg cells are not protected by ovaries, as in flowering plants. [4] Gymnosperms are divided into 12 families of trees, shrubs and woody vines. [5] Sequoiadendron giganteum, the giant redwood, is the largest tree in the world, and Sequoia sempervirens, the coastal redwood, is the tallest. [6]
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 the three relict genera: Gnetum (family Gnetaceae), Welwitschia (family Welwitschiaceae), and Ephedra (family ...
A mature female big-cone pine (Pinus coulteri) cone, the heaviest pine cone A young female or seed cone on a Norway spruce (Picea abies) Immature male or pollen cones of Swiss pine (Pinus cembra) A conifer cone or, in formal botanical usage, a strobilus, pl.: strobili, is a seed-bearing organ on gymnosperm plants, especially in conifers and cycads.
Phyllocladus aspeniifolius is a large, conical conifer in the family Podocarpaceae. The trunk is erect with horizontal branches. True leaves appear at the seedling stage and are fine and needle-like. Mature leaves are reduced to minute, brown scales.
Of the species studied so far, Gnetum have photosynthetic and transpiration capacities which are considerably lower than those of other seed plants, due to 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. [5]
The euphyllophytes consist of two lineages, the spermatophytes or seed plants such as flowering plants (angiosperms) and gymnosperms (conifers and related groups), and the Polypodiophytes or ferns, as well as a number of extinct fossil groups. [4]