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Gnetophytes
Gnetophyta () 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 Ephedraceae). Fossilized pollen attributed to a close relative of ''Ephedra'' has been dated as far back as the Early Cretaceous. Though diverse in the Early Cretaceous, only three families, each containing a single genus, are still alive today. The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements, a system of conduits that transport water within the plant, similar to those found in flowering plants. Because of this, gnetophytes were once thought to be the closest gymnosperm relatives to flowering plants, but more recent molecular studies have brought this hypothesis into question. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cycad
Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow very slowly and live very long. Because of their superficial resemblance, they are sometimes mistaken for Arecaceae, palms or ferns, but they are not closely related to either group. Cycads are gymnosperms (naked-seeded), meaning their fertilization, unfertilized seeds are open to the air to be directly fertilized by pollination, as contrasted with angiosperms, which have enclosed seeds with more complex fertilization arrangements. Cycads have very specialized pollinators, usually a specific species of beetle. Both male and female cycads bear cones (strobilus, strobili), somewhat similar to conife ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gymnosperm
The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, ''Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμνόσπερμος ( el, γυμνός, translit=gymnos, lit=naked, label=none and el, σπέρμα, translit=sperma, lit=seed, label=none), literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds (called ovules in their unfertilized state). The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or solitary as in yew, ''Torreya'', ''Ginkgo''. Gymnosperm lifecycles involve alternation of generations. They have a dominant diploid sporophyte phase and a reduced haploid gametophyte phase which is dependent on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Welwitschia
''Welwitschia'' is a monotypic gymnosperm genus, comprising solely the distinctive ''Welwitschia mirabilis'', endemic to the Namib desert within Namibia and Angola. ''Welwitschia'' is the only living genus of the family Welwitschiaceae and order Welwitschiales in the division Gnetophyta, and is one of three living genera in Gnetophyta, alongside ''Gnetum'' and ''Ephedra''. Informal sources commonly refer to the plant as a "living fossil". Naming ''Welwitschia'' is named after the Austrian botanist and doctor Friedrich Welwitsch, who described the plant in Angola in 1859. Welwitsch was so overwhelmed by the plant that he, "could do nothing but kneel down ..and gaze at it, half in fear lest a touch should prove it a figment of the imagination." Joseph Dalton Hooker of the Linnean Society of London, using Welwitsch's description and collected material along with material from the artist Thomas Baines who had independently recorded the plant in Namibia, described the species. Wel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ephedra Distachya (female Plant In Bloom)
''Ephedra distachya'' is a shrub in the family Ephedraceae that stands about 25 cm to 50 cm high. The shrub grows in many parts of the world, including southern and central Europe and western and central Asia. Its local names include ''somlatha''. Subspecies #''Ephedra distachya'' subsp. ''distachya'' – central + southern Europe, southwestern + central Asia #''Ephedra distachya'' subsp. ''helvetica'' (C.A.Mey.) Asch. & Graebn. – Switzerland, France, Italy, Slovenia, Austria History ''Ephedra'' is part of a group of plants called ‘gnetophytes’. These plants have hardly changed in the past 100 million years, and are thought to be relics of an ancient flora. The leaves of ''Ephedra'' are tiny and scale-like. Gnetophyte leaves evolved independently from leaves in flowering plants. ''Ephedra'' produces the alkaloid ephedrine, which has been shown to interfere with insect thermoregulation and may also have effects on insect neurotransmitters. This may be the method ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Welwitschia Mirabilis
''Welwitschia'' is a monotypic gymnosperm genus, comprising solely the distinctive ''Welwitschia mirabilis'', endemic to the Namib desert within Namibia and Angola. ''Welwitschia'' is the only living genus of the family Welwitschiaceae and order Welwitschiales in the division Gnetophyta, and is one of three living genera in Gnetophyta, alongside ''Gnetum'' and ''Ephedra''. Informal sources commonly refer to the plant as a "living fossil". Naming ''Welwitschia'' is named after the Austrian botanist and doctor Friedrich Welwitsch, who described the plant in Angola in 1859. Welwitsch was so overwhelmed by the plant that he, "could do nothing but kneel down ..and gaze at it, half in fear lest a touch should prove it a figment of the imagination." Joseph Dalton Hooker of the Linnean Society of London, using Welwitsch's description and collected material along with material from the artist Thomas Baines who had independently recorded the plant in Namibia, described the species. Wel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malesia
Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalayan and Australasian realms, and also a phytogeographical floristic region in the Paleotropical Kingdom. It has been given different definitions. The World Geographical Scheme for Recording Plant Distributions split off Papuasia in its 2001 version. Floristic province Malesia was first identified as a floristic region that included the Malay Peninsula, the Malay Archipelago, New Guinea, and the Bismarck Archipelago, based on a shared tropical flora derived mostly from Asia but also with numerous elements of the Antarctic flora, including many species in the southern conifer families Podocarpaceae and Araucariaceae. The floristic region overlaps four distinct mammalian faunal regions. The first edition of the World Geographical Scheme for Recording Plant Distributions (WGSRPD) used this definition, but in the second edition of 2001, New Guinea and the Bismarck Archipelago were r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnetum Gnemon
''Gnetum gnemon'' is a species of ''Gnetum'' native to southeast Asia and the western Pacific Ocean islands, from Mizoram and Assam in India, south and east through Indonesia and Malaysia to the Philippines, Fiji, and Hawaii in the United States. Common names include gnetum, joint fir, two leaf, melinjo, belinjo, bago, and tulip. Description It is a small to medium-size tree (unlike most other ''Gnetum'' species, which are lianas), growing to 15–22 m tall and with a trunk diameter of up to. 40 cm (16 in). The leaves are evergreen, opposite, 8–20 cm long and 3–10 cm broad, entire, emerging bronze-coloured, maturing glossy dark green. The fruit-like female strobilus consist of little but skin and a large nut-like seed 2–4 cm long inside. Male strobili are small, arranged in long stalks, and are often mistaken for flowers.This species of gymnosperm can be easily confused for an angiosperm due to the fruit-like female strobili, broad leaves and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Woody Plant
A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposite to herbaceous plants that die back to the ground until spring. Characteristics Woody plants are usually either trees, shrubs, or lianas. These are usually perennial plants whose stems and larger roots are reinforced with wood produced from secondary xylem. The main stem, larger branches, and roots of these plants are usually covered by a layer of bark. Wood is a structural tissue that allows woody plants to grow from above ground stems year after year, thus making some woody plants the largest and tallest terrestrial plants. Woody plants, like herbaceous perennials, typically have a dormant period of the year when growth does not take place, in colder climates due to freezing temperatures and lack of daylight during the winter months, in subtropical and tropical climates due to the dry sea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pollination
Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, and bats; water; wind; and even plants themselves, when self-pollination occurs within a closed flower. Pollination often occurs within a species. When pollination occurs between species, it can produce hybrid offspring in nature and in plant breeding work. In angiosperms, after the pollen grain (gametophyte) has landed on the stigma, it germinates and develops a pollen tube which grows down the style until it reaches an ovary. Its two gametes travel down the tube to where the gametophyte(s) containing the female gametes are held within the carpel. After entering an ovum cell through the micropyle, one male nucleus fuses with the polar bodies to produce the endosperm tissues, while the other fuses with the ovule to produce the embr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsporangia
Microsporangia are sporangia that produce microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants that have heterosporic life cycles, such as seed plants, spike mosses and the aquatic fern genus ''Azolla''. In gymnosperms and angiosperm anthers, the microsporangia produce microsporocytes, the microspore mother cells, which then produce four microspores through the process of meiosis. Microsporocytes are produced in the microsporangia of gymnosperm cones and the anthers of angiosperms. They are diploid microspore mother-cells, which then produce four haploid microspores through the process of meiosis. These become pollen grains, within which the microspores divide twice by mitosis to produce a very simple gametophyte. Heterosporous plants that produced microspores in microsporangia and megaspores in separate megasporangia evolved independently in several plant groups during the Devonian period. Fossils of these plants sho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ovule
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center. The female gametophyte — specifically termed a ''megagametophyte''— is also called the ''embryo sac'' in angiosperms. The megagametophyte produces an egg cell for the purpose of fertilization. The ovule is a small structure present in the ovary. It is attached to the placenta by a stalk called a funicle. The funicle provides nourishment to the ovule. Location within the plant In flowering plants, the ovule is located inside the portion of the flower called the gynoecium. The ovary of the gynoecium produces one or more ovules and ultimately becomes the fruit wall. Ovules are attached to the placenta in the ovary through a stalk-like structure known as a ''funiculus'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture. Typically, they also look different from the parts of the flower, such as the petals or sepals. A plant having bracts is referred to as bracteate or bracteolate, while one that lacks them is referred to as ebracteate and ebracteolate, without bracts. Variants Some bracts are brightly-coloured and serve the function of attracting pollinators, either together with the perianth or instead of it. Examples of this type of bract include those of ''Euphorbia pulcherrima'' (poinsettia) and ''Bougainvillea'': both of these have large colourful bracts surrounding much smaller, less colourful flowers. In grasses, each floret (flower) is enclosed in a pair of papery bracts, called the lemma (lower bract) and p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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