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Witch's Broom
Witch's broom or witches' broom is a deformity in a woody plant, typically a tree, where the natural structure of the plant is changed. A dense mass of shoots grows from a single point, with the resulting structure resembling a broom or a bird's nest. It is sometimes caused by pathogens. Diseases with symptoms of witches' broom, caused by phytoplasmas or basidiomycetes, are economically important in a number of crop plants, including the cocoa tree ''Theobroma cacao'', jujube (''Ziziphus jujuba'') and the timber tree '' Melia azedarach''. Causes A tree's characteristic shape, or habit, is in part the product of auxins, hormones which control the growth of secondary apices. The growth of an offshoot is limited by the auxin, while that of the parent branch is not. In cases of witch's broom, the normal hierarchy of buds is interrupted, and apices grow indiscriminately. This can be caused by cytokinin, a phytohormone which interferes with growth regulation. The phenomenon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mistletoe
Mistletoe is the common name for obligate hemiparasitic plants in the order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they extract water and nutrients from the host plant. The name mistletoe originally referred to the species '' Viscum album'' (European mistletoe, of the family Santalaceae in the order Santalales); it is the only species native to the British Isles and much of Europe. A related species with red rather than white fruits, '' Viscum cruciatum'', occurs in Southwest Spain and Southern Portugal, as well as in Morocco in North Africa and in southern Africa. The genus ''Viscum'' is not native to North America, but ''Viscum album'' was introduced to Northern California in 1900. The eastern mistletoe native to North America, '' Phoradendron leucarpum'', belongs to a distinct genus of the family Santalaceae. European mistletoe has smooth-edged, oval, evergreen leaves borne in pairs along the woo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phytohormone
Plant hormone (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, from embryogenesis, the regulation of organ size, pathogen defense, stress tolerance and through to reproductive development. Unlike in animals (in which hormone production is restricted to specialized glands) each plant cell is capable of producing hormones. Went and Thimann coined the term "phytohormone" and used it in the title of their 1937 book. Phytohormones occur across the plant kingdom, and even in algae, where they have similar functions to those seen in higher plants. Some phytohormones also occur in microorganisms, such as unicellular fungi and bacteria, however in these cases they do not play a hormonal role and can better be regarded as secondary metabolites. Characteristics The word hormone is derived from Greek, meaning ''set in motion''. Plant hormones affect gene ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phyllody
Phyllody is the abnormal development of floral parts into leafy structures. It is generally caused by phytoplasma or virus infections, though it may also be because of environmental factors that result in an imbalance in plant hormones. Phyllody causes the affected plant to become partially or entirely sterile, as it is unable to normally produce flowers. The condition is also known as phyllomorphy or frondescence; though the latter may sometimes refer more generically to foliage, leafiness, or the process of leaf growth. Phyllody is usually differentiated from floral virescence, wherein the flowers merely turn green in color but otherwise retain their normal structure. However, floral virescence and phyllody (along with witch's broom and other growth abnormalities), commonly occur together as symptoms of the same diseases. The term chloranthy is also often used for phyllody (particularly flowers exhibiting complete phyllody, such that it resembles leaf buds more than flowers), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moniliophthora Perniciosa
''Moniliophthora perniciosa'' (previously ''Crinipellis perniciosa'') is a fungus that causes " witches' broom disease" (WBD) of the cocoa tree ''T. cacao''. This pathogen is currently limited to South America, Panama and the Caribbean, and is perhaps one of the best-known cocoa diseases, thought to have co-evolved with cocoa in its centre of origin (first recorded in the Brazilian Amazon in 1785). This fungus is hemibiotroph, with two characteristic phases: biotrophic (expanding and infecting, on living tissue) and saprotrophic (producing basidiospores, on necrotic tissue). The biotrophic stage, and what triggers its switch to a saprotrophic stage, are still not understood. Hosts and symptoms ''Moniliophthora perniciosa'' can infect a number of hosts. Generally, ''M. perniciosa'' infects tropical host plants, and host plants in the Upper Amazon River basin on the eastern side of the Andes. ''M. perniciosa'' is now known to comprise four different biotypes (C, S, L and H), ea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melampsora
''Melampsora'' is a genus of Basidiomycota Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Ba ... fungi. ''Melampsora'' species are plant pathogens. Subtaxa ''Melampsora'' contains the following species and formae speciales: *'' Melampsora abietis-canadensis'' *'' Melampsora abietis-caprearum'' *'' Melampsora abietis-populi'' *'' Melampsora aecidioides'' *'' Melampsora albertensis'' *'' Melampsora allii-populina'' *'' Melampsora americana'' *'' Melampsora amygdalinae'' *'' Melampsora apocyni'' *'' Melampsora arctica'' *'' Melampsora bigelowii'' *'' Melampsora caprearum'' *'' Melampsora chelidonii-pierotii'' *'' Melampsora coleosporioides'' *'' Melampsora epiphylla'' *'' Melampsora epitea'' *'' Melampsora euonymi-caprearum'' *'' Melampsora euphorbiae'' *'' Melampso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Longan Witches Broom-associated Virus
''Longan witches broom-associated virus'' (LWBD or LWBaV) is a species of positive-sense single-stranded RNA virus that has not been assigned to a genus within the family ''Potyviridae''. It is thought to be the cause of witch's broom in longan (''Dimocarpus longan''), a large tropical tree from southeastern Asia of economic value. Longan witches broom disease is a condition that was first described in 1941. The virus was found in symptomatic plants and absent in healthy plants, but not all of Koch's postulates have been fulfilled. Names The official name for the species of virus is ''Longan witches broom-associated virus'', properly written in italics, capitalized, and with no apostrophe. Within the species, there is one noted member virus, longan witches' broom-associated virus, which is not italicized or capitalized, but does include the apostrophe. In Chinese it is called () or (). In Vietnamese the disease is called , , , , and . Phylogeny ''Longan witches broom-associa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forest Pathology
Forest pathology is the research of both biotic and abiotic maladies affecting the health of a forest ecosystem, primarily fungal pathogens and their insect vectors. It is a subfield of forestry and plant pathology. Forest pathology is part of the broader approach of forest protection. Insects, diseases and severe weather events damaged about 40 million ha of forests in 2015, mainly in the temperate and boreal domains. Abiotic factors There are a number of abiotic factors which affect the health of a forest, such as moisture issues like drought, winter-drying, waterlogging resulting from over-abundance or lack of precipitation such as hail, snow, rain. Wind is also an important abiotic factor as windthrow (the uprooting or breaking of trees due to high winds) causes an obvious and direct loss of stability to a forest or its trees. Often, abiotic factors and biotic factors will affect a forest at the same time. For example, if wind speed is 80 km per hour then many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epicormic Shoot
An epicormic shoot is a shoot growing from an epicormic bud, which lies underneath the bark of a trunk, stem, or branch of a plant. Epicormic buds lie dormant beneath the bark, their growth suppressed by hormones from active shoots higher up the plant. Under certain conditions, they grow into active shoots, such as when damage occurs to higher parts of the plant, or light levels are increased following removal of nearby plants. Epicormic buds and shoots occur in many woody species, but are absent from many others, such as most conifers. Function Human horticultural practices that exploit epicormic growth rely on plants that have epicormic budding capabilities for regenerative function in response to crown damage, such as through wind or fire. Epicormic shoots are the means by which trees regrow after coppicing or pollarding, where the tree's trunk or branches are cut back on a regular cycle. These forestry techniques cannot be used on species which do not possess strong e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant Development
Important structures in plant development are buds, shoots, roots, leaves, and flowers; plants produce these tissues and structures throughout their life from meristems located at the tips of organs, or between mature tissues. Thus, a living plant always has embryonic tissues. By contrast, an animal embryo will very early produce all of the body parts that it will ever have in its life. When the animal is born (or hatches from its egg), it has all its body parts and from that point will only grow larger and more mature. However, both plants and animals pass through a phylotypic stage that evolved independently and that causes a developmental constraint limiting morphological diversification. According to plant physiologist A. Carl Leopold, the properties of organization seen in a plant are emergent properties which are more than the sum of the individual parts. "The assembly of these tissues and functions into an integrated multicellular organism yields not only the characterist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northern Flying Squirrel
The northern flying squirrel (''Glaucomys sabrinus'') is one of three species of the genus '' Glaucomys'', the only flying squirrels found in North America.Walker EP, Paradiso JL. 1975. ''Mammals of the World''. Baltimore: Johns Hopkins University Press.Forsyth A. 1999. ''Mammals of North America: Temperate and Arctic Regions''. Willowdale: Firefly Books. They are found in coniferous and mixed coniferous forests across much of Canada, from Alaska to Nova Scotia, and south to the mountains of North Carolina and west to Utah in the United States. They are light brown with pale underparts and grow to a length of . They are proficient gliders but uncoordinated walkers on the ground. They feed on a variety of plant material as well as tree sap, fungi, insects, carrion, bird eggs and nestlings. They mostly breed once a year in a cavity lined with lichen or other soft material. Except when they have young, they change nests frequently, and in winter a number of individuals may huddle tog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898,Dimmock p. 4 more than 9,000 virus species have been described in detail of the millions of types of viruses in the environment. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. The study of viruses is known as virology, a subspeciality of microbiology. When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent particles, or ''virions'', consisting of (i) the genetic ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nematode
The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant- parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a broad range of environments. Less formally, they are categorized as Helminths, but are taxonomically classified along with arthropods, tardigrades and other moulting animals in the clade Ecdysozoa, and unlike flatworms, have tubular digestive systems with openings at both ends. Like tardigrades, they have a reduced number of Hox genes, but their sister phylum Nematomorpha has kept the ancestral protostome Hox genotype, which shows that the reduction has occurred within the nematode phylum. Nematode species can be difficult to distinguish from one another. Consequently, estimates of the number of nematode species described to date vary by author and may change rapidly over time. A 2013 survey of animal biodiversity published in the mega ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
