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Rachis
In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the ''rachis'' usually forms the supporting axis of the body and is then called the spine or vertebral column. ''Rachis'' can also mean the central shaft of pennaceous feathers. In the gonad of the invertebrate nematode '' Caenorhabditis elegans'', a rachis is the central cell-free core or axis of the gonadal arm of both adult males and hermaphrodites where the germ cells have achieved pachytene and are attached to the walls of the gonadal tube. The rachis is filled with cytoplasm. In botany In plants, a rachis is the main axis of a compound structure. It can be the main stem of a compound leaf, such as in ''Acacia'' or ferns, or the main, flower-bearing portion of an inflorescence above a supporting peduncle. Where it subdivides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leaf
A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form the shoot system. In most leaves, the primary photosynthetic 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. Most leaves are flattened and have distinct upper (adaxial) and lower ( abaxial) surfaces that differ in color, hairiness, the number of stomata (pores that intake and output gases), the amount and structure of epicuticular wax and other features. Leaves are mostly green in color due to the presence of a compound called chlorophyll that is essential for photosynthesis as it absorbs light ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peduncle (botany)
In botany, a peduncle is a stalk supporting an inflorescence or a solitary flower, or, after fecundation, an infructescence or a solitary fruit. The peduncle sometimes has bracts (a type of cataphylls) at nodes. The main axis of an inflorescence above the peduncle is the rachis. There are no flowers on the peduncle but there are flowers on the rachis. When a peduncle arises from the ground level, either from a compressed aerial stem or from a subterranean stem (rhizome, tuber, bulb, corm), with few or no bracts except the part near the rachis or receptacle, it is referred to as a scape. The acorns of the pedunculate oak are borne on a long peduncle, hence the name of the tree. See also *Pedicel (botany) *Scape (botany) In botany, a scape is a peduncle arising from a subterranean or very compressed stem, with the lower internodes very long and hence few or no bracts except the part near the rachis or receptacle. Typically it takes the form of a long, leafles ... Re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed on the axis of a plant. The modifications can involve the length and the nature of the internodes and the phyllotaxis, as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes. One can also define an inflorescence as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern. The stem holding the whole inflorescence is called a peduncle. The major axis (incorrectly referred to as the main stem) above the peduncle bearing the flowers or secondary branches is called the rachis. The stalk of each flower in the inflorescence is called a pedicel. A flower that is not part of an inflorescence is called a solitary flower and its stalk is al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
History Of Agriculture
Agriculture began independently in different parts of the globe, and included a diverse range of Taxon, taxa. At least eleven separate regions of the Old World, Old and New World were involved as independent centers of origin. The development of agriculture about 12,000 years ago changed the way humans lived. They switched from nomadic hunter-gatherer lifestyles to permanent settlements and farming. Wild cereal, grains were collected and eaten from at least 105,000 years ago. However, domestication did not occur until much later. The earliest evidence of small-scale cultivation of edible grasses is from around 21,000 BC with the Ohalo II people on the shores of the Sea of Galilee. By around 9500 BC, the eight Neolithic founder crops – emmer wheat, einkorn wheat, barley, hulled barley, peas, lentils, Vicia ervilia, bitter vetch, chickpeas, and flax – were cultivated in the Levant. Rye may have been cultivated earlier, but this claim remains controversial. Ric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pennaceous Feather
The pennaceous feather is a type of feather present in most modern birds and in some other species of maniraptoriform dinosaurs. Description A pennaceous feather has a stalk or quill. Its basal part, called a ''calamus'', is embedded in the skin. The calamus is hollow and has pith formed from the dry remains of the feather pulp, and the calamus opens below by an ''inferior umbilicus'' and above by a ''superior umbilicus''. The stalk above the calamus is a solid ''rachis'' having an umbilical groove on its underside. Pennaceous feathers have a rachis with ''vanes'' or ''vaxillum '' spreading to either side. These vanes are composed of a high number of flattened ''barbs'', that are connected to one another with ''barbules''. The barbules are tiny strands that criss-cross on the flattened sides of the barbs. This forms a miniature velcro-like mesh that holds all the barbs together, stabilizing the vanes. Pennaceous feathers on the wing, and elsewhere that stresses related to fligh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shattering (agriculture)
In agriculture, shattering is the dispersal of a crop's seeds upon their becoming ripe. From an agricultural perspective this is generally an undesirable process, and in the history of crop domestication several important advances have involved a mutation in a crop plant that reduced shattering—instead of the seeds being dispersed as soon as they were ripe, the mutant plants retained the seeds for longer, which made harvesting much more effective. Non-shattering phenotype is one of the prerequisites for plant breeding especially when introgressing valuable traits from wild varieties of domesticated crops. A particularly important mutation that was selected very early in the history of agriculture removed the "brittle rachis" problem from wheat. A ripe head ("ear") of wild-type wheat is easily shattered into dispersal units when touched, or blown by the wind, because during ripening a series of abscission layers forms that divides the rachis into short segments, each attached to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stipe (botany)
In botany, a stipe is a stalk that supports some other structure. The precise meaning is different depending on which taxonomic group is being described. file:Helicteres-Yucatán-Flowers.jpg, The long stipe of a '' Helicteres'' flower. file:Helicteres-Yucatán-Fruits.jpg, remains as each flower forms a fruit. In the case of ferns, the stipe is only the petiole from the rootstock to the beginning of the leaf tissue, or lamina. The continuation of the structure within the lamina is then termed a rachis. In flowering plants, the term is often used in reference to a stalk that sometimes supports a flower's ovary. In orchids, the stipe or caudicle is the stalk-like support of the pollinia. It is a non-viscid band or strap connecting the pollinia with the viscidium (the viscid part of the rostellum or beak). A stipe is also a structure found in organisms that are studied by botanists but that are no longer classified as plants. It may be the stem-like part of the thallus of a mus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acacia
''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus name is New Latin, borrowed from the Greek (), a term used by Dioscorides for a preparation extracted from the leaves and fruit pods of ''Vachellia nilotica'', the original type of the genus. In his ''Pinax'' (1623), Gaspard Bauhin mentioned the Greek from Dioscorides as the origin of the Latin name. In the early 2000s it had become evident that the genus as it stood was not monophyletic and that several divergent lineages needed to be placed in separate genera. It turned out that one lineage comprising over 900 species mainly native to Australia, New Guinea, and Indonesia was not closely related to the much smaller group of African lineage that contained ''A. nilotica''—the type species. This meant that the Australasian lineage (by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turkey Feather Close Sdetwiler
Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula in Southeast Europe. It shares borders with the Black Sea to the north; Georgia to the northeast; Armenia, Azerbaijan, and Iran to the east; Iraq to the southeast; Syria and the Mediterranean Sea to the south; the Aegean Sea to the west; and Greece and Bulgaria to the northwest. Cyprus is located off the south coast. Turks form the vast majority of the nation's population and Kurds are the largest minority. Ankara is Turkey's capital, while Istanbul is its largest city and financial centre. One of the world's earliest permanently settled regions, present-day Turkey was home to important Neolithic sites like Göbekli Tepe, and was inhabited by ancient civilisations including the Hattians, Hittites, Anatolian peoples, Mycenaean Greeks, Persians ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buddleja Paniculata
''Buddleja paniculata'' is a species of flowering plant in the figwort family Scrophulariaceae, endemic to a wide upland area from northern India to Bhutan, growing along forest margins, in thickets, and on rocky slopes at elevations of . The species was named by Wallich and introduced to the UK in 1823 as seed sent by Major Madden from the Himalayas to the Glasnevin Botanic Garden.Stuart, D. (2006). ''Buddlejas''. RHS Plant Collector Guide. Timber Press, Oregon, USA. Description ''Buddleja paniculata'' is a variable deciduous shrub or tree of bushy habit, occasionally reaching high. The sparse terminal panicles comprise white or pale lilac flowers, some forms pleasantly scented, others not, from December to mid-spring. The bright green lanceolate leaves are opposite, up to in length, and covered in fine hairs. 2''n'' = 38.Chen, G, Sun, W-B, & Sun, H. (2007). Ploidy variation in Buddleja L. (Buddlejaceae) in the Sino - Himalayan region and its biogeographical implications. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fern
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except the lycopods, and differ from mosses and other bryophytes by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the branched sporophyte is the dominant phase. Ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns. They produce coiled fiddleheads that uncoil and expand into fronds. The group includes about 10,560 known extant species. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate (Polypodiidae) and eusporangiate ferns, the latter group including horsetails, whisk ferns, marattioid ferns, and ophioglossoid ferns. Ferns first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeologists
Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landscapes. Archaeology can be considered both a social science and a branch of the humanities. It is usually considered an independent academic discipline, but may also be classified as part of anthropology (in North America – the four-field approach), history or geography. Archaeologists study human prehistory and history, from the development of the first stone tools at Lomekwi in East Africa 3.3 million years ago up until recent decades. Archaeology is distinct from palaeontology, which is the study of fossil remains. Archaeology is particularly important for learning about prehistoric societies, for which, by definition, there are no written records. Prehistory includes over 99% of the human past, from the Paleolithic until the adve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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