|
Diaspore (botany)
In botany, a diaspore is a plant dispersal unit consisting of a seed or spore plus any additional tissues that assist dispersal. Examples of such additional structures includes elaiosomes, fruits, pseudofruits or arils, as well as pappi. In a few plants, the diaspore is a tumbleweed and comprises most of the plant. Diaspores are common in weedy and ruderal species. Collectively, diaspores, seeds, and spores that have been modified for migration are known as ''disseminules''. __TOC__ Role in dispersal A diaspore of seed plus elaiosome is a common adaptation to seed dispersal by ants (myrmecochory). This is most notable in Australian and South African sclerophyll plant communities. Typically, ants carry the diaspore to their nest, where they may eat the elaiosome and discard the seed, and the seed may subsequently germinate. A diaspore of seed(s) plus fruit is common in plants dispersed by frugivores. Fruit-eating bats typically carry the diaspore to a favorite perch, wher ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Taraxacum Ruderalia Dandelion Clock
A, or a, is the first letter and the first vowel letter of the Latin alphabet, used in the modern English alphabet, and others worldwide. Its name in English is '' a'' (pronounced ), plural ''aes''. It is similar in shape to the Ancient Greek letter alpha, from which it derives. The uppercase version consists of the two slanting sides of a triangle, crossed in the middle by a horizontal bar. The lowercase version is often written in one of two forms: the double-storey and single-storey . The latter is commonly used in handwriting and fonts based on it, especially fonts intended to be read by children, and is also found in italic type. In English, '' a'' is the indefinite article, with the alternative form ''an''. Name In English, the name of the letter is the ''long A'' sound, pronounced . Its name in most other languages matches the letter's pronunciation in open syllables. History The earliest known ancestor of A is ''aleph''—the first letter of the Phoenician ... [...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] |
Foxtail (diaspore)
A foxtail is a spikelet or cluster of a grass, that serves to disperse its seeds as a unit. Thus, the foxtail is a type of diaspore or plant dispersal unit. Some grasses that produce a foxtail are themselves called "foxtail", also "spear grass". They can become a health hazard for dogs, cats, and other domestic animals, and a nuisance for people. Sources The name "foxtail" is applied to a number of grasses that have bushy spikes of spikelets that resemble the tail of a fox. Not all of these are hazardous; most of the hazardous ones are in the genus ''Hordeum'', and are also called "wild barley". Grasses known as foxtails include: * '' Alopecurus'' (foxtail grasses — the scientific name literally means "fox tail") * '' Bromus madritensis'' (foxtail brome) * '' Hordeum jubatum'' (foxtail barley) * ''Setaria'' (foxtail millets) Other grasses also produce hazardous spikelets. The spikelets are sometimes called foxtails, even though the grasses are not. Structure All foxta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glume
In botany, a glume is a bract (leaf-like structure) below a spikelet in the inflorescence (flower cluster) of grass Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and spe ...es (Poaceae) or the flowers of sedges (Cyperaceae). There are two other types of bracts in the spikelets of grasses: the lemma and palea. In grasses, two bracts known as "glumes" form the lowermost organs of a spikelet (there are usually two but one is sometimes reduced; or rarely, both are absent). Glumes may be similar in form to the lemmas, the bracts at the base of each floret. In sedges, by contrast, a glume is a scale at the base of each flower in a spikelet. References {{reflist Plant morphology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caryopsis
In botany, a caryopsis () is a type of simple fruit—one that is monocarpellate (formed from a single carpel) and indehiscent (not opening at maturity) and resembles an achene, except that in a caryopsis the pericarp is fused with the thin seed coat. The caryopsis is popularly called a grain and is the fruit typical of the family Poaceae (or Gramineae), which includes wheat, rice, and maize. The term ''grain'' is also used in a more general sense as synonymous with cereal (as in "cereal grains", which include some non-Poaceae). Considering that the fruit wall and the seed are intimately fused into a single unit, and the caryopsis or grain is a dry fruit, little concern is given to technically separating the terms ''fruit'' and ''seed'' in these plant structures. In many grains, the " hulls" to be separated before processing are flower bracts. Etymology The name ''caryopsis'' is derived from the Greek words and ( and ), meaning 'nut' and 'having the appearance of', respec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grass
Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivated in lawns and pasture. The latter are commonly referred to collectively as grass. With around 780 genera and around 12,000 species, the Poaceae is the fifth-largest :plant families, plant family, following the Asteraceae, Orchidaceae, Fabaceae and Rubiaceae. The Poaceae are the most economically important plant family, including staple foods from domesticated cereal crops such as maize, wheat, rice, oats, barley, and millet for people and as forage, feed for livestock, meat-producing animals. They provide, through direct human consumption, just over one-half (51%) of all dietary energy; rice provides 20%, wheat supplies 20%, maize (corn) 5.5%, and other grains 6%. Some members of the Poaceae are used as building materials ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Desert
A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the land surface of the Earth is arid or Semi-arid climate, semi-arid. This includes much of the Polar regions of Earth, polar regions, where little precipitation occurs, and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location. Deserts are formed by weathering processes as large variations in temperature between day and night strain the Rock (geology), rocks, which consequently break in pieces. Although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter, and the resulting frag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steppe
In physical geography, a steppe () is an ecoregion characterized by grassland plains without closed forests except near rivers and lakes. Steppe biomes may include: * the montane grasslands and shrublands biome * the tropical and subtropical grasslands, savannas, and shrublands biome * the temperate grasslands, savannas, and shrublands biome A steppe is usually covered with grass and shrubs, depending on the season and latitude. The term ''steppe climate'' denotes a semi-arid climate, which is encountered in regions too dry to support a forest, but not dry enough to be a desert. Steppes are usually characterized by a semi-arid or continental climate. Temperature extremes can be recorded in the summer of up to and in winter of down to . Besides this major seasonal difference, fluctuations between day and night are also significant: in both the highlands of Mongolia and northern Nevada, can be reached during the day with sub-freezing readings at night. Steppes ave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tumbleweed
A tumbleweed is a structural part of the above-ground anatomy of a number of species of plants. It is a diaspore that, once mature and dry, detaches from its root or stem and rolls due to the force of the wind. In most such species, the tumbleweed is in effect the entire plant apart from the root system, but in other plants, a hollow fruit or inflorescence might detach instead. Xerophyte tumbleweed species occur most commonly in steppe and arid ecosystems, where frequent wind and the open environment permit rolling without prohibitive obstruction. Apart from its primary vascular system and roots, the tissues of the tumbleweed structure are dead; their death is functional because it is necessary for the structure to degrade gradually and fall apart so that its seeds or spores can escape during the tumbling, or germinate after the tumbleweed has come to rest in a moist location. In the latter case, many species of tumbleweed open mechanically, releasing their seeds as they swel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drift Fruit
__NOTOC__ Drift seeds (also sea beans) and drift fruits are seeds and fruits adapted for long-distance dispersal by water. Most are produced by tropical trees, and they can be found on distant beaches after drifting thousands of miles through ocean currents. This method of propagation has helped many species of plant such as the coconut colonize and establish themselves on previously barren islands. Consequently, drift seeds and fruits are of interest to scientists who study these currents. In botanical terminology, a drift fruit is a kind of diaspore, and drift seeds and fruits are disseminules. Sources of drift seeds * '' Caesalpinia bonduc'' – grey nickernut * '' Caesalpinia major'' – yellow nickernut * ''Carapa guianensis'' – crabwood (New World tropics) * '' Entada gigas'' – seaheart, (New World tropics) * '' Entada rheedii'' – snuff box sea bean, from the tropics of the Indian Ocean * '' Erythrina fusca'' – bucayo (pantropical) * '' Erythrina variegata'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wind
Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption (electromagnetic radiation), absorption of solar energy between the climate zones on Earth. The study of wind is called anemology. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet (Coriolis effect). Within the tropics and subtropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can prevail. Winds are commonly classified by their scale (spatial), spatial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
