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The mature seed comprises the embryo and the remains of the female gametophyte, which serves as a food supply, and the seed coat. [32] Gymnosperms ordinarily reproduce by sexual reproduction, and only rarely express parthenogenesis. [33] Sexual reproduction in gymnosperms appears to be required for maintaining long-term genomic integrity. [33]
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 ...
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.
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.
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]
Page information; Get shortened URL; ... Conifers (8 C, 26 P) Cycads (5 C, ... Pages in category "Gymnosperms" The following 4 pages are in this category, out of 4 ...
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 ]