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Aster Yellows
Aster yellows is a chronic, systemic plant disease caused by several bacteria called phytoplasma. The aster yellows phytoplasma (AYP) affects 300 species in 38 families of broad-leaf herbaceous plants, primarily in the aster family, as well as important cereal crops such as wheat and barley. Symptoms are variable and can include phyllody, virescence, chlorosis, stunting, and sterility of flowers. The aster leafhopper vector, ''Macrosteles quadrilineatus'', moves the aster yellows phytoplasma from plant to plant.Davis, M. R. & Raid, R. N., eds. Compendium of Umbelliferous Crop Diseases. St. Paul: The American Phytopathological Society. 2002. pp. 58-59. Its economic burden is primarily felt in the carrot (''Daucus carota'' ssp.'' sativus'') crop industry, as well as the nursery industry. No cure is known for plants infected with aster yellows.Hudelson, Brian. Aster Yellows. University of Wisconsin Garden Facts. 2006. Infected plants should be removed immediately to limit the cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carrot
The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in color, though purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild carrot, ''Daucus carota'', native to Europe and Southwestern Asia. The plant probably originated in Persia and was originally cultivated for its leaves and seeds. The most commonly eaten part of the plant is the taproot, although the stems and leaves are also eaten. The domestic carrot has been selectively bred for its enlarged, more palatable, less woody-textured taproot. The carrot is a biennial plant in the umbellifer family, Apiaceae. At first, it grows a rosette of leaves while building up the enlarged taproot. Fast-growing cultivars mature within three months (90 days) of sowing the seed, while slower-maturing cultivars need a month longer (120 days). The roots contain high quantities of alpha- and beta-carotene, and are a good source of vitamin A, vitamin K, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Onion
An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onion which was classified as a separate species until 2010. Its close relatives include garlic, scallion, leek, and chive. This genus also contains several other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion (''Allium fistulosum''), the tree onion (''A.'' × ''proliferum''), and the Canada onion (''Allium canadense''). The name ''wild onion'' is applied to a number of ''Allium'' species, but ''A. cepa'' is exclusively known from cultivation. Its ancestral wild original form is not known, although escapes from cultivation have become established in some regions. The onion is most frequently a biennial or a perennial plant, but is usually treated as an annual and harvested in its f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Food Plant Pathogens And Diseases
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or stimulate growth. Different species of animals have different feeding behaviours that satisfy the needs of their unique metabolisms, often evolved to fill a specific ecological niche within specific geographical contexts. Omnivorous humans are highly adaptable and have adapted to obtain food in many different ecosystems. The majority of the food energy required is supplied by the industrial food industry, which produces food with intensive agriculture and distributes it through complex food processing and food distribution systems. This system of conventional agriculture relies heavily on fossil fuels, which means that the food and agricultural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacterial Plant Pathogens And Diseases
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic relationsh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phyllody On Coneflower With Aster Yellows
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] |
Stylet (anatomy)
A stylet is a hard, sharp, anatomical structure found in some invertebrates. For example, the word ''stylet'' or stomatostyle is used for the primitive piercing mouthparts of some nematodes and some nemerteans. In these groups the stylet is a hardened protrusible opening to the stomach. These stylets are adapted for the piercing of cell walls and usually function by providing the operative organism with access to the nutrients contained within the prey cell. The mouthparts of tardigrades, diptera and aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...s are also called stylets. In octopodes, the stylets are internal, needle-like bent rods within the mantle, the vestigial remnants of an external shell. References Nematode anatomy {{Animal-anatomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fecundity
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to produce offspring, measured by the number of gametes (eggs), seed set, or asexual propagules. Superfecundity refers to an organism's ability to store another organism's sperm (after copulation) and fertilize its own eggs from that store after a period of time, essentially making it appear as though fertilization occurred without sperm (i.e. parthenogenesis). Human demography Human demography considers only human fecundity, at its culturally differing rates, while population biology studies all organisms. The term ''fecundity'' in population biology is often used to describe the rate of offspring production after one time step (often annual). In this sense, fecundity may include both birth rates and survival of young to that time step. Whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prokaryotes
A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Connections". Pearson Education. San Francisco: 2003. In the two-empire system arising from the work of Édouard Chatton, prokaryotes were classified within the empire Prokaryota. But in the three-domain system, based upon molecular analysis, prokaryotes are divided into two domains: ''Bacteria'' (formerly Eubacteria) and ''Archaea'' (formerly Archaebacteria). Organisms with nuclei are placed in a third domain, Eukaryota. In the study of the origins of life, prokaryotes are thought to have arisen before eukaryotes. Besides the absence of a nucleus, prokaryotes also lack mitochondria, or most of the other membrane-bound organelles that characterize the eukaryotic cell. It was once thought that prokaryotic cellular components within the cytopla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemiptera
Hemiptera (; ) is an order (biology), order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, Reduviidae, assassin bugs, Cimex, bed bugs, and shield bugs. They range in size from to around , and share a common arrangement of piercing-sucking Insect mouthparts, mouthparts. The name "true bugs" is often limited to the suborder Heteroptera. Entomologists reserve the term ''bug'' for Hemiptera or Heteroptera,Gilbert Waldbauer. ''The Handy Bug Answer Book.'' Visible Ink, 1998p. 1. which does not include other arthropods or insects of other orders such as Ant, ants, Bee, bees, Beetle, beetles, or Butterfly, butterflies. In some variations of English, all Terrestrial animal, terrestrial arthropods (including non-insect arachnids, and myriapods) also fall under the Colloquialism, colloquial understanding of ''bug''. Many insects with "bug" in their common name, especially in American English, belo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aster Leafhopper
''Macrosteles quadrilineatus'', the aster leafhopper or six-spotted leafhopper, is a leafhopper species in the genus '' Macrosteles'', found in the United States. It is the vector of aster yellows disease, which affects various vegetable plants, weeds and ornamental plants. Description The aster leafhopper is a small species, with males reaching about in length and females about . The fore-wings are greyish-green while the abdomen is yellowish-green. Six pairs of minute black spots or streaks on the head give the insect its alternative name of six-spotted leafhopper. Ecology In the United States, strong southerly winds in the spring carry adults northwards to the Mid West and northern parts of the country, and these insects usually arrive earlier and exceed in number the resident insects that have been overwintering there, mostly on grasses and cereals. Eggs are laid on a wide range of host plants which include grasses and clovers, corn, oats, rye, carrots and various weeds. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 can a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Celery
Celery (''Apium graveolens'') is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, leaves or hypocotyl are eaten and used in cooking. Celery seed powder is used as a spice. Description Celery leaves are pinnate to bipinnate with rhombic leaflets long and broad. The flowers are creamy-white, in diameter, and are produced in dense compound umbels. The seeds are broad ovoid to globose, long and wide. Modern cultivars have been selected for either solid petioles, leaf stalks, or a large hypocotyl. A celery stalk readily separates into "strings" which are bundles of angular collenchyma cells exterior to the vascular bundles. Wild celery, ''Apium graveolens'' var. ''graveolens'', grows to tall. Celery is a biennial plant that occurs around the globe. It produces flowers and seeds only during its second year. The first cul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
