A primordium ( / p r aɪ ˈ m ɔːr d i ə m / ; pl. : primordia ; synonym: anlage ) in embryology , is an organ or tissue in its earliest recognizable stage of development. Cells of the primordium are called primordial cells . A primordium is the simplest set of cells capable of triggering growth of the would-be organ and the initial foundation from which an organ is able to grow. In flowering plants, a floral primordium gives rise to a flower.
41-486: Although it is a frequently used term in plant biology, the word is used in describing the biology of all multicellular organisms (for example: a tooth primordium in animals, a leaf primordium in plants or a sporophore primordium in fungi.) Plants produce both leaf and flower primordia cells at the shoot apical meristem (SAM). Primordium development in plants is critical to the proper positioning and development of plant organs and cells. The process of primordium development
82-562: A "fantasy" (game) that solely relies on the skill being mastered, rather than the other way around. These fantasies also tend to possess a few characteristics, such as (1) understanding that the fantasy and the skill that is being learned are inextricably linked, (2) the fantasy context and the instructional content being provided have an intrinsic and continuous link, and (3) endogenous fantasies tend to include more intellectually challenging and captivating content compared to exogenous fantasies. In materials science , an exogenous property of
123-739: A bulge. This bulging is caused by slower and less anisotropic , or directionally dependent, growth. Primordia initiation is the precursor for the start of a primordium, and typically confers new growth (either flowers or leaves) in plants once fully mature. In pines , the leaf primordia develop into buds, which eventually elongate into shoots, then stems, then branches. Though primordia are typically only found in new flower and leaf growth, root primordia in plants can also be found, but are typically referred to as lateral root primordium or adventitious roots . The process of lateral root primordium initiation has been studied in Arabidopsis thaliana , though
164-436: A cascade signaling effect, by triggering ARF and Aux/IAA protein functions. PUCHI genes act as a transcriptional regulator of lateral root primordium development by controlling its cell division during this stage. Early events in leaf development fall into three main processes: 1. Initiation of the leaf primordium 2. Establishment of dorsoventrally (abaxial-adaxial polarity ) which
205-434: A higher surface area to volume ratio, are hosts to a higher diversity of fungicolous fungi than pileate sporocarps are. Exogenous In a variety of contexts, exogeny or exogeneity (from Greek ἔξω éxō 'outside' and -γένεια -géneia 'to produce') is the fact of an action or object originating externally. It contrasts with endogeneity or endogeny, the fact of being influenced within
246-619: A large degree in academic mycology as well, identification of higher fungi is based on the features of the sporocarp. The largest known fruitbody is a specimen of Phellinus ellipsoideus (formerly Fomitiporia ellipsoidea ) found on Hainan Island , part of China . It measures up to 10.85 metres ( 35 + 1 ⁄ 2 feet) in length and is estimated to weigh between 450 and 760 kilograms (990 and 1,680 pounds). A wide variety of animals feed on epigeous and hypogeous fungi. The mammals that feed on fungi are as diverse as fungi themselves and are called mycophages. Squirrels and chipmunks eat
287-424: A large impact on plant primordium development because of their effect on gene regulation. Lateral roots are one of the most important tissues in a plant's anatomical structure. They provide physical support and uptake water and nutrients for growth. Before the emergence of lateral roots in the morphogenetic process, a new lateral root primordium which consists of primordial cells is formed. Localized cell divisions in
328-495: A much greater amount than the human body can handle. On the opposite end, endogenous obesity refers to obesity caused by disorders or issues outside an imbalance of food intake itself, which include genetic disorders , interruption of thyroid functions, and other syndromic disorders. In relation to cancer, carcinogens are exogenous factors, in which these are made up of various factors (chemical, biological, physical), causing cancer after having entering through several routes of
369-461: A role in a three-way symbiotic relationship with small marsupials and Australian Eucalyptus forests. In Eucalyptus forests, hypogeous sporocarp dispersal is positively affected by fires. After a fire, most if not all epigeous sporocarps are wiped out, leaving hypogeous sporocarps to be the primary source of fungi for small marsupials. The ability of hypogeous fungi to resist disasters, such as fire, could be due to their evolved ability to survive
410-471: A substantial impact on the structure of the knowledge generated. Through the perspective of Piaget , learning was known as the individual's former structures accommodated to those imposed by its current environment. The individual's accommodation is directed by the environment, which provides the structures to which the individual must adapt. In attentional psychology , exogenous stimuli are external stimuli without conscious intention. An example of this
451-499: A system. In an economic model , an exogenous change is one that comes from outside the model and is unexplained by the model. Such changes of an economic model from outside factors can include the influence of technology, in which this had previously been noted as an exogenous factor, but has rather been noted as a factor that can depict economic forces as a whole. In economic sociology , Project IDEA (Interdisciplinary Dimensions of Economic Analysis) gave notion to understanding
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#1732800908890492-407: A traditional regression model . An exogenous contrast agent , in medical imaging for example, is a liquid injected into the patient intravenously that enhances visibility of a pathology, such as a tumor . An exogenous factor is any material that is present and active in an individual organism or living cell but that originated outside that organism, as opposed to an endogenous factor. In
533-432: Is correlated with the error term in the econometric model, while an exogenous variable is not. However, exogenous variables aid in the explanation of endogenous variable variances. In the preset group, it is typical to include historical values of endogenous variables. Exogenous variables are independent of the model's disturbance term , since they are preset. They meet the same conditions as explanatory variables do in
574-654: Is Auxin. Leaf primordia are specified as auxin maxima in a flanking region of the SAM following the rules of phyllotaxy. Phyllotactic spiral patterns, as observed in Arabidopsis , have an unequal auxin distribution between left and right sides, resulting in asymmetrical growth of leaf laminas. For example, in clockwise phyllotactic spiral patterns, the left side will grow more than the right side and vice versa for counterclockwise phyllotactic spiral patterns. Leaf initiation requires high intracellular auxin concentration and
615-415: Is a multicellular structure on which spore-producing structures , such as basidia or asci , are borne. The fruitbody is part of the sexual phase of a fungal life cycle , while the rest of the life cycle is characterized by vegetative mycelial growth and asexual spore production. The sporocarp of a basidiomycete is known as a basidiocarp or basidiome , while the fruitbody of an ascomycete
656-505: Is attention drawn to a flashing light in the periphery of vision . In geography , exogenous processes all take place outside the Earth and all the other planets . Weathering , erosion , transportation and sedimentation are the main exogenous processes. Asides from climate, exogenous geographic factors are able to contribute to the overall process of distribution, including densities of populations and urbanizations of certain areas in
697-416: Is established with bulging of the primordia 3. Development of a marginal meristem Lateral organ and leaf development initiation is dependent upon the structure of the shoot apical meristem (SAM). In the center of the SAM, there is a central zone of many indeterminate, undifferentiated cells where cell division is infrequent. Cells divide more frequently in the peripheral zones flanking
738-507: Is generated by directional auxin transport through the SAM. Once in the meristem, developing organ primordia act as a sink, absorbing and depleting auxin from the surrounding tissue. The accumulation of auxin in the developing organ primordia induces the formation of new leaf primordium. The SAM continues to produce leaf primordia regularly on its flanks throughout the vegetative phase. Sporocarp (fungi) The sporocarp (also known as fruiting body , fruit body or fruitbody ) of fungi
779-436: Is highest. There is still much to understand about the genes involved in primordium development. Leaf primordia are groups of cells that will form into new leaves. These new leaves form near the top of the shoot and resemble knobby outgrowths or inverted cones. Flower primordia are the little buds we see at the end of stems, from which flowers will develop. Flower primordia start off as a crease or indentation and later form into
820-419: Is intricately regulated by a set of genes that affect the positioning, growth and differentiation of the primordium. Genes including STM (shoot meristemless) and CUC (cup-shaped cotyledon) are involved in defining the borders of the newly formed primordium. The plant hormone auxin has also been implicated in this process, with the new primordium being initiated at the placenta, where the auxin concentration
861-527: Is known as an ascocarp . Many shapes and morphologies are found in both basidiocarps and ascocarps; these features play an important role in the identification and taxonomy of fungi. Fruitbodies are termed epigeous if they grow on the ground, while those that grow underground are hypogeous . Epigeous sporocarps that are visible to the naked eye, especially fruitbodies of a more or less agaricoid morphology, are often called mushrooms . Epigeous sporocarps have mycelia that extend underground far beyond
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#1732800908890902-399: Is noted to assume that knowledge comes from an individual's environment, which is assumed to be learned. Because an active individual is expected to be participating in the abstraction of knowledge from its environment, practical guidance of this result of participation remains the most crucial feature of directing the learning process. The structure of the individual's operating environment has
943-533: Is regulated via Auxin concentration, and because of this, exogenous Auxin is required to increase the transcription of PUCHI genes. This allows us to infer that the PUCHI gene must be downstream to Auxin signaling. One method used to test the theory that PUCHI is responsible for LRP development, was by using Arabidopsis Thaliana accession col as the wild type (WT) strain, and isolating the PUCHI-1-mutant from
984-446: Is that the composition of fungi in the diet of Tasmanian bettong was positively correlated with body condition and growth rates of pouch young. Ectomycorrhizal or hypogeous fungi form a symbiotic relationship with small mycophagous mammals. Hypogeous sporocarps depend on small fungivorous mammals to disperse their spores since they are underground and cannot utilize wind dispersal like epigeous sporocarps. Underground fungi also play
1025-566: The LR initiation and primordium development in the LR formation process, but cytokinin negatively regulates the growth of the LR. However, it is not fully understood the full mechanisms of how these different hormones affect the transport, signaling, or biosynthesis of the others. The PUCHI gene (specifically an Auxin regulated AP2/EREBP gene), plays a vital role in coordinating the organization/pattern of cell division during lateral root primordium (LRP) development, in Arabidopsis thaliana. PUCHI expression
1066-482: The Pericycle give rise to the lateral root primordia. This pattern of growth gives rise to a bundle of tissue. The subsequent accumulation of cell division and enlargement in this bundle of tissue gives rise to a new structure known as the root primordium. The root primordium emerges as a new lateral rootlet by creating its own root cap and apex. Both genetic and physiological studies point to the importance of Auxin in
1107-407: The SAM and are incorporated into leaf primordia, also referred to as founder cells for leaves. Cells are recruited from the flanks of the shoot apical meristem which initiates the development of leaf primordia. Signals propagated in the epidermis initiate primordia growth in directions away from the cotyledons (in dicotyledonous plants) in simple patterns, known as phyllotaxis . Phyllotaxis are
1148-520: The T-DNA insertion. The function of the PUCHI gene was demonstrated by using the PUCHI-1 mutant (using Arabidopsis Thaliana as the model plant), which if backcrossed three times to Arabidopsis Thaliana accession col (WT), it was demonstrated to affect lateral root and flower primordium development by stunting LR growth. One of the many theories out there, is that Auxin promotes downstream PUCHI expression via
1189-421: The arrangement of leaves on an axis or stem and can either be arranged in a spiral or whorl pattern moving out radially by continually dividing cells at their central edges. Phyllotactic patterns determine plant architecture and the positions of where new leaves will develop can be easily predicted by observing the locations of existing leaf primordia. The key instructive signal for phyllotactic pattern formation
1230-462: The body. DNA introduced to cells via transfection or viral transduction is an exogenous factor. Exogenous factors in DNA, particularly DNA damage , are more known as environmental factors that cause progression in the impairment of DNA. Such exogenous factors would be different chemical agents, ionizing radiation (IR), and ultraviolet radiation (UV). These factors penetrate the deeper layers of
1271-448: The body. In philosophy , the origins of existence of self , or the identity of self, emanating from, or sustaining, outside the natural or influenced realm, are exogenous. Exogenous constructivism prioritizes the reconstruction of structures that have already been created in the environment, which is based from a mechanical metaphor, and greatly reflects off of Bandura 's social learning theory . Overall, exogenous constructivism
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1312-427: The cell, causing great damage, with either apoptosis or senescence occurring, further leading to arrested or altered development and aging of the organism causing neurological disorders and cancer . In medicine , exogenous factors are seen in both pathogens and therapeutics . Exogenous factors can be included in the type of obesity where there is an imbalance of food and metabolism , in which one consumes
1353-468: The digestive systems of animals in order to distribute. Sporocarps can also serve as a food source for other fungi. Sporocarps can be hosts to diverse communities of fungicolous fungi. Short-lived sporocarps are more often hosts to fungicolous fungi than are long-lived sporocarps, which may have evolved more investment in defense mechanisms and tend to have less water content than their short-lived counterparts. Resupinate sporocarps, sporocarps that have
1394-726: The exogenous factors that play a role within economic theory . Developed from the International Social Science Council (ISSC) in the year of 1982, Project IDEA was founded to gather ideas from economists and sociologists in order to conceptualize what economic sociology incorporates, as they have sought to understand why these two fields have been estranged from each other. Such exogenous factors in economic theory include laws placed in economic systems by governments, ranks of social classes in populations, and preferences based on social factors of an individual. In econometrics , an endogenous random variable
1435-495: The greatest variety of fungi, but there are many other mammals that also forage on fungi, such as marsupials , mice , rats , voles , lemmings , deer , shrews , rabbits , weasels , and more. Some animals feed on fungi opportunistically, while others rely on them as a primary source of food. Hypogeous sporocarps are a highly nutritious primary food source for some small mammals like the Tasmanian bettong . Evidence of this
1476-415: The growth and development of plants. Auxin concentrations affect mitosis, cell expansion, as well as cell differentiation. There is a lot of current research being conducted to explain the role that it assists in the process of plant primordium. It is believed to control these processes by binding to a specific receptor on plant cells and influences gene expression. It affects transcription factors that control
1517-448: The mother sporocarp. There is a wider distribution of mycelia underground than sporocarps above ground. Hypogeous fungi are usually called truffles or false truffles . There is evidence that hypogeous fungi evolved from epigeous fungi. During their evolution , truffles lost the ability to disperse their spores by air currents, and propagate instead by animal consumption and subsequent defecation. In amateur mushroom hunting , and to
1558-415: The origins of diseases , exogenous factors, namely those that are factors of inflammation or stress , such as overexertion , overeating , and extreme feelings of emotions of grief or anger, all contribute to exhaustion or modifications in genes . An accumulation of such stressors affect the immune system by disrupting the amount of communication that occurs between the immune system and other areas of
1599-432: The process in other angiosperms is still under analysis. Primordia are initiated by local cell division and enlargement on the shoot apical meristem. At least in wheat plants, leaf primordium initiation rates increase with increasing ambient temperature, and the leaf number of some varieties decrease with increasing daylength. Auxin is a group of plant hormones , or phytohormones, that plays a key role in almost all areas of
1640-456: The upregulation or downregulation of auxin genes that relate to growth. This has led researchers to believe that auxin accumulation as well as decreases in auxin levels might control different phases of primordium development. Auxin concentration gradients are necessary to initiate and continue primordial growth. Higher concentrations allow them to bind to cells and results in downstream effects that lead to primordial growth. Auxins have
1681-512: The world. Exogeneity is proposed to ultimately cause geographic considerations to be rejected. In ludology , the study of games, an exogenous item is anything outside the game itself. Therefore, an item in a massively multiplayer online game would have exogenous value if people were buying it with real world money rather than in-game currency (though its in-game cost would be endogenous ). Noted as exogenous fantasy, one may also refer to this term as extrinsic stimuli or "fantasy"; these describe