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The gymnosperms (/ ˈ dʒ ɪ m n ə ˌ s p ɜːr m z,-n oʊ-/ ⓘ nə-spurmz, -noh-; lit. ' revealed seeds ') are a group of woody, perennial seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae [2] The term gymnosperm comes from the ...
The gymnosperms consist of five orders of seed plants: Cupressales, Cycadales, Ginkgoales, Gnetales and Pinales. [a] They developed more than 350 million years ago, long before flowering plants, according to the fossil record. The name comes from the Greek for "naked seed"; the egg cells are not protected by ovaries, as in flowering plants. [4]
For one, both male and female cycads are gymnosperms and bear cones (strobili), while palms are angiosperms and so flower and bear fruit. The mature foliage looks very similar between both groups, but the young emerging leaves of a cycad resemble a fiddlehead fern before they unfold and take their place in the rosette, while the leaves of palms ...
The microsporangia of gymnosperms develop in pairs toward the bases of the scales, which are therefore called microsporophylls. Each of the microsporocytes in the microsporangia undergoes meiosis, producing four haploid microspores. These develop into pollen grains, each consisting of four cells and, in conifers, a pair of external air sacs.
Gnetum is a genus of gymnosperms, the sole genus in the family Gnetaceae within the Gnetophyta.They are tropical evergreen trees, shrubs and lianas.Unlike other gymnosperms, they possess vessel elements in the xylem.
All gymnosperms are woody plants. Their stems are similar in structure to woody dicots except that most gymnosperms produce only tracheids in their xylem, not the vessels found in dicots. Gymnosperm wood also often contains resin ducts. Woody dicots are called hardwoods, e.g. oak, maple and walnut.
Diagram showing the alternation of generations between a diploid sporophyte (bottom) and a haploid gametophyte (top) Alternation of generations (also known as metagenesis or heterogenesis) [1] is the predominant type of life cycle in plants and algae.
Cross section of ovule in gymnosperms and angiosperms. Gymnosperm pollen is produced in microsporangia borne on the scales of the male cone or microstrobilus.In most species, the plants are wind-pollinated, and the pollen grains of conifers have air bladders that provide buoyancy in air currents.