Abaixo todos os artigos disponíveis, em ordem decrescente de data:
| Polyploidy as a chromosomal component of stochastic noise: variable scalar multiples of the diploid chromosome complement in the invertebrate species Girardia schubarti from Brazil [08/3/2018] |
| Chromosome stoichiometry, a form of genetic plasticity, specifically refers to variation in the standard diploid genomic composition of an individual or species. In the present work, freshwater planarians (Girardia schubarti) were analyzed to recognize variations in chromosomal stoichiometry especially of complete ploidal change between specimens, within specimens and between cells within specimens and any relations they might have with selected components of phenotypic plasticity. Homoploid polyploids for the group reached rational scalar multiples (e.g. tetraploids) or irrational scalar multiples (e.g. triploids). Karyotypic mosaics emerged where individual cells presented polyploid multiples in arithmetic and geometric progressions. Ploidal multiplicity, a chromosomal component of stochastic noise, had positive phenotypic effects (increased dimensions) on morphologic criteria of body length, body width and dorsal surface reflecting a significant genotypic plasticity (GP) and robust phenotypic plasticity (PP). Variable but significant association of genotypic plasticity with robust phenotypic variance suggests kinetics of phenotypic homeostasis that is species-specific permitting phenotypic adaptability to environmental variables by means of GP. That association is diminished, deactivated or lost in more advanced and more complex organisms. [Esconder Sinopse]
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| Permutation of ground state phylloid buds and flowers from a paleobotanically reverted recombinant of psophocarpus [15/10/2012] |
| Paleochronic (anachronic) reversion is an atavism (transition) of angiosperm flowers, a transmutation that nullifies the sexual reproductive dynamic reducing the reproductive system to a phylloid state. This seldom remains stable as a permutative stage usually follows spatially transforming anatomic zones (i.e. whorls and bracts), regions within zones (e.g. floral whorls), or even sites within regions (e.g. carpel components). Permutation can be augmented, accompanied or followed by vascularization, deadnation and/or spiralling in a scenario of transformations. This research focused on 51 reverted floral specimens from a reverted recombinant of Psophocarpus tetragonolobus. The recombinant, verified phenotypically as homozygous recessive for a master homeotic gene (srs) responsible for this reversion, was also dominant for four major “reversion dependent genes”. Transition presented (in planta) the two stages characteristic of paleochronic reversion; transmutation and permutation. A general chronology for floral permutation occurred. Parallel and tangent carpel clefts underwent distancing of central portions of these clefts by means of a “webbing” function. Decompression permutation occurred at the inter-zonal (i.e. pericladial stalk), inter-regional (i.e. inter-bracts stem) and inter-whorl (e.g. gynophore and/or cupule-like structure) anatomic levels. Spiralling of carpels frequently occurred as did vascularization and deadnation of carpels to a lesser extent. The order of events presented a sequence that was “paleoanachronic”; a development of anachronic characteristics whose succession was variable yet significantly ordered. [Esconder Sinopse]
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| Chromosome polymorphism and complements in populations of Girardia especies from Southern Brazil [06/7/2008] |
| The karyotypes of four species of freshwater triclads of the genus Girardia, i.e. G. schubarti, G. tigrina, G. anderlani, and G. biapertura, from populations of different localities of the Rio Grande do sul State, in southern Brazil, were analyzed. The karyotype of G. biapertura is presented for the first time. Three basic compleents of 4, 8, and 9 chromosomes were found. Diploids, triploids, or mixoploids (2n/3n) specimens were frequently detected in these populations. The basic chromosomal complement of n=9 was verified in two different species, presenting a large acrocentric chromosome which is rare in the family dugesiidae. An intra and interspecific chromosomal variability was also detected and its evolutionary implications are discussed. [Esconder Sinopse]
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| Forestry in Belize, Part II: Modern Times and Transition [05/9/2007] |
| If the birth of the Modern Forest Industry in Belize can be traced to the basic thrusts and incentives suggested in the Humel Report of 1921, then the acknowledged maturity of that industry and its integration with conservation can be traced to the British Honduras Forest Policy Report of 2 September, 1954. In ten basic interrelated points this report emphasized the major positions set forth in 1921 and further enunciated the relations between forestry, soil and water conservation, and sound ecosystem preservation (8). [Esconder Sinopse]
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| Forestry in Belize, Part I:Beginnings of Modern Forestry and Agriculture, 1921 to 1954 [05/9/2007] |
| Lumbering is the oldest industry in Belize. It began with the logwood (Haematoxlon campechianum) cutters of the mid-1600's but latter shifted emphasis to mahogany (Swietenia, Carapa and Tapirira species). Still later cedar (Cedrella mexicana) and pine (Pinus species) took on important but secondary status to mahogany. The rapid growth and regeneration of most wood species (as measured in their life cycles), coupled with a sparce population of people in Belize throughout its history, allowed lumbering to develop as the dominant industry with little concern for formal intensive forest management. It was an industry requiring a rather minimal capital investment yet turning out large volumes of raw and milled lumber for foreign and domestic markets. [Esconder Sinopse]
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| The Art of the Carbonaro [04/9/2007] |
The forests of Belize yield an array of products to fill the need of men and women both within the country and throughout the world; raw materials for construction, carving, food, fuel, industry and medicine. Some of these products can be used directly as they come from the forest (fruits, nuts, bamboo, fuel wood). Others must be processed by sawing, finishing or milling as in the case of lumber, furniture and chicle. The collection of each raw material and its preparation into a final product requires a special skill. The wood cutter, shipwright and furniture maker all work with the same raw material, lumber, but each uses special skill to fashon that lumber into a different product unique to his trade.
Every trade has its skill, indeed an art that varies in its degree of precision and in the amount of time required to master it. One of the finest and most complex of these skills is that of the Carbonaro, the charcoal-maker; who is, just as the work "carbonaro" implies, a maker of carbon. His trade involves using fire to change wood, especially hardwood into charcoal. [Esconder Sinopse]
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| The Cattle Industry of Belize [03/9/2007] |
| The development of a cattle industry in any area, temperate or tropical, historically has occurred in three progressively complex steps of usage. These three uses are work, meat, and milk. Each step requires a more intense application of the principles of herdsmanship and animal husbandry, and a more intensive incorporation of all resources to achieve an ever increasing level of production per animal, per laborer and per unit of land. The pattern of development in Belize follows these three steps. [Esconder Sinopse]
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| Genetic aspects of flower reversion in the winged bean (Psophocarpus tetragonolobus [L.] DC [03/9/2007] |
| Flower buds of the winged bean (Psophocarpus tetragonolobus [L.] DC) growing in Teresina, Piauí, Brazil reverted from their normal sexual reproductive function to a photosynthetic vegetative function. In comparison with normal flowers, reverted flowers were characterized by a transition from a tetragonolobanous to a digonolobanous form (100% of samples observed) and by virescence of flower parts (99.4% of samples obwerved). Reversion was further characterized by vivipary which depends on the degree of evocation (i.e. induction) of vegetative buds to flower buds and on foliation of reverted ovules in flowers. Statistical analysis of data from field experiments indicated a single gene, in the homozygous recessive form in all reverted individuals, to be the genetic basis of this reversion phenomenon. [Esconder Sinopse]
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| Meristem Identity on Anatomic Sections of Reverted Homeotic Segregants of the Winged Bean... [03/9/2007] |
Meristem Identity on Anatomic Sections of Reverted Homeotic Segregants of the Winged Bean Psophocarpus Tetragonolobus (L.) DC Under Laboratory Conditions.
Laboratory investigations on anatomic sections from reverted segregants of the winged bean Psophocarpus tetragonolobus (L.) DC, homozygous for a recessive homeotic gene in its activated state, revealed two forms of extra-morphologic meristem identity; rhizogenous and vegetative manifest in three steps: extra-vegetative, extra-rhizogenous, and both. This identity, in terms of number of structures at specific anatomic sites, showed significant concentrations at the ovary (i.e. carpel) or fourth floral whorl regions, plus the pre-whorl bracts regions. These results suggest that even in morphologically transformed sections of reverted segregants, anatomic and organ regions (e.g. the four floral whorls) maintain some definitive function or functions.
[Esconder Sinopse]
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| Qualitative Aspects of Extra-Morphological Activity On Anatomic Sections of Reverted Homeotic.... [17/8/2007] |
Qualitative Aspects of Extra-Morphological Activity On Anatomic Sections Of Reverted Homeotic Segregants of the Winged Bean Psophocarpus Tetragonolobus (L.) DC Under Laboratory Conditions
Laboratory studies on anatomical sections from reverted segregants of the winged bean Psophocarpus tetragonolobus (L.) DC, homozygous for a recessive homeotic gene in its activated state, revealed four stages of morphological transformation. Normal floral specimens reverted from the sexual reproductive function to an asexual photosynthetic function with no further activity (previous analysis). In laboratory, reverted specimens could remain inactive or show three types of extra-morphological activity. These types were: extra-vegetative activity (33.71%), extra-rhizogenous activity (35.96%), both these forms of extra-morphological activity (30.34%). This activity, in terms of sites on anatomic sectons, showed significant occurrence at the pre-whorl bract regions, plus two of the four floral whorl regions, i.e. the calyx (sepals) or first whorl and the ovary (carpel) or fourth whorl. Data shows that the one gene already identified width this morphological transformation, besides being homeotic and recessive, is also a natural morphological mutant thats is nonepigenetic. [Esconder Sinopse]
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| Persistence of Anatomic Sections from Reverted Homeotic Segregants of The Winged Bean [17/8/2007] |
| Laboratory tests concerning anatomic sections, both morphologically reverted and normal, from reverted segregants, homozygous for a recessive homeotic gene in the winged bean revealed significant differences in metabolic persistence as measured by treatment time span. The six major classes of anatomic sections studied included normal flowers and stems, plus the four recognized abnormal classes: reverted stems, fusions, reverted flowers and reverted flower buds. Persistence increased in significant steps according to: determinate or indeterminate growth, reverted or non-reverted condition, extra-morphologically active or inactive condition, and purity of water as the medium of culture. [Esconder Sinopse]
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| Interorganismal Morphological Aspects of Flower and Bud Reversion in The Winged Bean [17/8/2007] |
| Morphologically reverted segregants, homozygous for a recessive homeotic mutant gene that permits reversion, field-grown in the tropical, semiarid, equatorial region of Teresina, Piauí, Brazil showed a valiable sequence of inter-organismal morphological characteristics associated with that reversion. Those characteristics and their sequence provide further information about this particular reversion phenomenon and its effects whick overall must be considered deleterious to populations and individuals that are homozygous for this gene. [Esconder Sinopse]
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| A phylloid ground state of reverted floral specimens of Psophocarpus [12/10/2004] |
| Recombinants of Psophocarpus tetragonolobus (L.) DC (Fabaceae), homozygous for a recessive allele of a master homeotic gene reverted from a normal photosynthetic, sexual reproductive nature to a vegetative, non-reproductive nature. This included transmutative transformation of floral meristems to a non-sexual phylloid floral ground state where the virescent organs maintained their identity but floral meristem identity was cancelled thus giving rise to a form of anachronic reversion. This was usually followed by a scenario of phyllotactic alterations involving the elongation of the floral axis which physically transformed flowers, in varying degrees of spatial permutations by the formation of ancestral floral structures, including gynophore and a pericladial stalk: a form of paleochronic reversion. Research verified that an allele of the master homeotic gene responsible for this phenomenon is a prerequisite to that scenario. Specific permutations are directly controlled by at least four additional homeotic genes recognized, defined and functionally characterized herein. Their qualitative functions (i.e. dominant or recessive) are responsible respectively for the carpel form, being either vascularized (VSCARP) or digonolobe (vscarp); the state of the gynophore being formed (GNF) or nascent (gnf); the state of the pericladial stalk being formed (PCL) or nascent (pcl) and the bracts position remaining parallel (BCT:PRL) at the calyx (or on the pericladial stalk) or being dislocated due to an interbractial stem formation between bracts (bct:prl). Results indicate that floral meristem identity once established can naturally be cancelled with little or no effect on floral organ identity. [Esconder Sinopse]
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