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Welwitschia
''Welwitschia'' is a monotypic genus of gnetophytes containing only the species ''Welwitschia mirabilis''. It is named after the Austrian botanist Friedrich Welwitsch, who documented the plant in the 1850s. In common use, it is sometimes referred to as the tree tumbo. It is native to Angola and Namibia, where it grows in the extreme conditions of the Namib desert, tolerating high heat and low precipitation. ''Welwitschia'' is the only living genus of the family Welwitschiaceae and order Welwitschiales, and is one of three extant genera of gnetophytes, alongside '' Gnetum'' and '' Ephedra''. ''Welwitschia'' is well known for its unique morphology. The plant only has two leaves that grow out of a large woody stem, dubbed a crown, and continue to grow over the plant's entire life. ''Welwitschia'' is one of the longest-living plants on Earth, with some individuals being thousands of years old. As such, the leaves can become quite large, often reaching several meters in length. L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Welwitschiaceae
Welwitschiaceae is a family of plants of the order Gnetales with one living species, '' Welwitschia mirabilis'', found in southwestern Africa. Three fossil genera have been recovered from the Crato Formation – late Aptian ( Lower Cretaceous) strata located in the Araripe Basin in northeastern Brazil, with one of these also being known from the early Late Cretaceous (Cenomanian-Turonian) Akrabou Formation of Morocco. Taxonomy German naturalist Friedrich Markgraf coined the name Welwitschiaceae in 1926, which appeared in '' Die Natürlichen Pflanzenfamilien''. Most recent systems place the Welwitschiaceae in the gymnosperm order Gnetales. This order is most closely related to the order Pinales, which includes all extant conifers. Genetic analyses indicate that the Gnetales arose from within the conifer group, and any morphological similarities between angiosperms and Gnetales have evolved separately. The ancestors of the extant gymnosperm orders—Gnetales, Coniferales, Cy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Welwitschiales
Welwitschiaceae is a family of plants of the order Gnetales with one living species, ''Welwitschia, Welwitschia mirabilis'', found in southwestern Africa. Three fossil genera have been recovered from the Crato Formation – late Aptian (Lower Cretaceous) strata located in the Araripe Basin in northeastern Brazil, with one of these also being known from the early Late Cretaceous (Cenomanian-Turonian) Akrabou Formation of Morocco. Taxonomy German naturalist Friedrich Markgraf coined the name Welwitschiaceae in 1926, which appeared in ''Die Natürlichen Pflanzenfamilien''. Most recent systems place the Welwitschiaceae in the gymnosperm order Gnetales. This order is most closely related to the order Pinales, which includes all extant conifers. Genetic analyses indicate that the Gnetales arose from within the conifer group, and any morphological similarities between angiosperms and Gnetales have evolved separately. The ancestors of the extant gymnosperm orders—Gnetales, Coniferal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnetophyta
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). The earliest unambiguous records of the group date to the Jurassic, and they achieved their highest diversity during the Early Cretaceous. The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements, a system of small tubes (xylem) 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, with many recent phylogenies finding them to be nested within the conifers. Though it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedrich Welwitsch
Friedrich Martin Josef Welwitsch (25 February 1806 – 20 October 1872) was an Austrian Empire, Austrian exploration, explorer and botany, botanist who in Angola was the first European to describe the plant ''Welwitschia, Welwitschia mirabilis''. His report received wide attention among the botanists and general public, comparable only to the discovery of two other plants in the 19th century, namely ''Victoria amazonica'' and ''Rafflesia arnoldii''.Strlič, Matija. "Dr. Friderik Velbič, 1806–1872". ''Proteus, the journal of the Natural Sciences Society of Slovenia''. Year 61, No. 9/10 (pp. 396-404). ISSN 0033-1805. In Angola, Welwitsch also discovered ''Rhipsalis baccifera'', the only cactus species naturally occurring outside the New World. It was found a few years later in Sri Lanka too, which reignited the now already one-and-a-half-century-old debate on the origin of cacti in Africa and Asia. At the time, the debate concluded with the conviction of numerous authors that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gymnosperm
The gymnosperms ( ; ) are a group of woody, perennial Seed plant, seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include Pinophyta, conifers, cycads, Ginkgo, and gnetophyta, gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in ( and ), and literally means '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 (botany), ovary. Gymnosperm seeds develop either on the surface of scales or Leaf, leaves, which are often modified to form Conifer cone, cones, or on their own as in Taxus, yew, ''Torreya'', and ''Ginkgo''. The life cycle of a gymnosperm involves alternation of generations, with a dominant diploid sporophyte phase, and a reduced haploid gam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Namib
The Namib ( ; ) is a coastal desert in Southern Africa. According to the broadest definition, the Namib stretches for more than along the Atlantic coasts of Angola, Namibia, and northwest South Africa, extending southward from the Carunjamba River in Angola, through Namibia and to the Olifants River (Western Cape), Olifants River in Western Cape, South Africa. The Namib's northernmost portion, which extends from the Angola-Namibia border, is known as Moçâmedes Desert, while its southern portion approaches the neighboring Kalahari Desert. From the Atlantic coast eastward, the Namib gradually ascends in elevation, reaching up to inland to the foot of the Great Escarpment, Southern Africa, Great Escarpment. Annual precipitation ranges from in the aridest regions to at the escarpment, making the Namib the only true desert in southern Africa. Having endured Desert climate, arid or Semi-arid climate, semi-arid conditions for roughly 55–80 million years, the Namib may be the old ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meristem
In cell biology, the meristem is a structure composed of specialized tissue found in plants, consisting of stem cells, known as meristematic cells, which are undifferentiated cells capable of continuous cellular division. These meristematic cells play a fundamental role in plant growth, regeneration, and acclimatization, as they serve as the source of all differentiated plant tissues and organs. They contribute to the formation of structures such as fruits, leaves, and seeds, as well as supportive tissues like stems and roots. Meristematic cells are totipotent, meaning they have the ability to differentiate into any plant cell type. As they divide, they generate new cells, some of which remain meristematic cells while others differentiate into specialized cells that typically lose the ability to divide or produce new cell types. Due to their active division and undifferentiated nature, meristematic cells form the foundation for the formation of new plant organs and the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnetum
''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. Some species have been proposed to have been the first plants to be insect-pollinated as their fossils occur in association with extinct pollinating scorpionflies. Molecular phylogenies based on nuclear and plastid sequences from most of the species indicate hybridization among some of the Southeast Asian species. Fossil-calibrated molecular-clocks suggest that the ''Gnetum'' lineages now found in Africa, South America and Southeast Asia are the result of ancient long-distance dispersal across seawater. Their leaves are rich in phytochemicals such as flavonoids and stilbenes. 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 c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ephedra (plant)
''Ephedra'' is a genus of gymnosperm shrubs. there were 77 recognized species. The various species of ''Ephedra'' are widespread in many arid regions of the world, ranging across southwestern North America, southern Europe, northern Africa, southwest and central Asia, northern China, and western South America. It is the only extant genus in its family, Ephedraceae, and order, Ephedrales, and one of the three living members of the division Gnetophyta alongside ''Gnetum'' and ''Welwitschia.'' In temperate climates, most ''Ephedra'' species grow on shores or in sandy soils with direct sun exposure. Common names in English include joint-pine, jointfir, Mormon-tea, or Brigham tea. The Chinese name for ''Ephedra'' species is ''mahuang'' (). ''Ephedra'' is the origin of the name of the stimulant ephedrine, which the plants contain in significant concentration. Description The family Ephedraceae, of which ''Ephedra'' is the only extant genus, are gymnosperms, and generally shrubs, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leaf
A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form the Shoot (botany), shoot system. In most leaves, the primary Photosynthesis, photosynthetic Tissue (biology), tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf, but in some species, including the mature foliage of ''Eucalyptus'', palisade mesophyll is present on both sides and the leaves are said to be isobilateral. The leaf is an integral part of the stem system, and most leaves are flattened and have distinct upper (Glossary of botanical terms#adaxial, adaxial) and lower (Glossary of botanical terms#abaxial, abaxial) surfaces that differ in color, Trichome, hairiness, the number of stomata (pores that intake and output gases), the amount and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herero Language
Herero (Otjiherero) is a Bantu language spoken by the Herero and Mbanderu peoples in Namibia and Botswana, as well as by small communities of people in southwestern Angola. There were speakers in these countries between 2015 and 2018. Distribution Its linguistic distribution covers a zone called Hereroland, which is constituted of the region of Omaheke along with the Otjozondjupa and Kunene Regions. The Himba people, who are related to the Herero and Mbanderu, speak a dialect very close to Otjiherero. Many Herero-speakers live in Windhoek, the capital of Namibia. Phonology Consonants The sounds /f s l/ are found in loanwords. Vowels Script Because of the translation of missionary Gottlieb Viehe (1839–1901) of the Bible into Herero, at the end of the 19th century, the spoken language was transcribed to an alphabet based on the Latin script. Father Peter Heinrich Brincker (1836–1904) translated several theological works and songs. Orthography * a - �* b - ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germination
Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, ferns, bacteria, and the growth of the pollen tube from the pollen grain of a seed plant. Seed plants Germination is usually the growth of a plant contained within a seed resulting in the formation of the seedling. It is also the process of reactivation of metabolic machinery of the seed resulting in the emergence of radicle and plumule. The seed of a vascular plant is a small package produced in a fruit or cone after the union of male and female reproductive cells. All fully developed seeds contain an embryo and, in most plant species some store of food reserves, wrapped in a seed coat. Dormant seeds are viable seeds that do not germinate because they require specific internal or environmental stimuli to resume growth. Und ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
