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Search Results: 1 - 10 of 18948 matches for " PAULO;BUCKERIDGE "
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Effects of light stress on the growth of the epiphytic orchid Cattleya forbesii Lindl. X Laelia tenebrosa Rolfe
STANCATO, GIULIO C.;MAZZAFERA, PAULO;BUCKERIDGE, MARCOS S.;
Brazilian Journal of Botany , 2002, DOI: 10.1590/S0100-84042002000200011
Abstract: considering the performance of cam epiphytes under high levels of radiation or in shaded environments, with growth rate proportional to light intensity, the objective of this work was to evaluate the effects of long-term light stress on the growth of a brazilian epiphytic orchid, cattleya forbesii lindl. x laelia tenebrosa rolfe. two groups of plants were used in the first experiment, one under 90% (@ 1,650 μmol.m-2.s-1) of photosynthetically active radiation (par) and the other maintained under 22.5% (@ 400 μmol.m-2.s-1). in the second experiment the diffusive resistance, transpiration rate and fluorescence levels were monitored for plants that were under 22.5% of par, under 90% and plants transferred from 22.5 to 90%. our results show that light intensity interfered with growth and development of this orchid. data on the changes in pseudobulb volume throughout the time course of growth suggest that water and reserves stored in the back shoots are translocated to the current shoot. regarding stomatal resistance, plants under 22.5% of par reached a largest stomatal aperture during the night, whereas those under 90% only after dawn. after transfer from 22.5% par to 90% par the ratio of fv/fm decreased from approximately 0.8 to 0.7. this suggests the limitation of photoprotection mechanisms in the leaf and the results observed after the transfer of plants from 22.5% to 90% reinforce the possibility that a photoinhibition is reflected in a decrease in growth rate.
Effects of light stress on the growth of the epiphytic orchid Cattleya forbesii Lindl. X Laelia tenebrosa Rolfe
STANCATO GIULIO C.,MAZZAFERA PAULO,BUCKERIDGE MARCOS S.
Brazilian Journal of Botany , 2002,
Abstract: Considering the performance of CAM epiphytes under high levels of radiation or in shaded environments, with growth rate proportional to light intensity, the objective of this work was to evaluate the effects of long-term light stress on the growth of a Brazilian epiphytic orchid, Cattleya forbesii Lindl. X Laelia tenebrosa Rolfe. Two groups of plants were used in the first experiment, one under 90% (@ 1,650 μmol.m-2.s-1) of Photosynthetically Active Radiation (PAR) and the other maintained under 22.5% (@ 400 μmol.m-2.s-1). In the second experiment the diffusive resistance, transpiration rate and fluorescence levels were monitored for plants that were under 22.5% of PAR, under 90% and plants transferred from 22.5 to 90%. Our results show that light intensity interfered with growth and development of this orchid. Data on the changes in pseudobulb volume throughout the time course of growth suggest that water and reserves stored in the back shoots are translocated to the current shoot. Regarding stomatal resistance, plants under 22.5% of PAR reached a largest stomatal aperture during the night, whereas those under 90% only after dawn. After transfer from 22.5% PAR to 90% PAR the ratio of Fv/Fm decreased from approximately 0.8 to 0.7. This suggests the limitation of photoprotection mechanisms in the leaf and the results observed after the transfer of plants from 22.5% to 90% reinforce the possibility that a photoinhibition is reflected in a decrease in growth rate.
Illuminating Our World: An Essay on the Unraveling of the Species Problem, with Assistance from a Barnacle and a Goose
John Buckeridge,Rob Watts
Humanities , 2012, DOI: 10.3390/h1030145
Abstract: In order to plan for the future, we must understand the past. This paper investigates the manner in which both naturalists and the wider community view one of the most intriguing of all questions: what makes a species special? Consideration is given to the essentialist view—a rigid perspective and ancient, Aristotelian perspective—that all organisms are fixed in form and nature. In the middle of the 19th century, Charles Darwin changed this by showing that species are indeed mutable, even humans. Advances in genetics have reinforced the unbroken continuum between taxa, a feature long understood by palaeontologists; but irrespective of this, we have persisted in utilizing the ‘species concept’—a mechanism employed primarily to understand and to manipulate the world around us. The vehicles used to illustrate this journey in perception are the barnacle goose (a bird), and the goose barnacle (a crustacean). The journey of these two has been entwined since antiquity—in folklore, religion, diet and even science.
The ongoing evolution of humanness: perspectives from Darwin to de Chardin
J. S. Buckeridge
South African Journal of Science , 2010, DOI: 10.4102/sajs.v105i11/12.126
Abstract: The nature of humanness is discussed from observations made by Aristotle in 4th-century Greece, through to those of Charles Darwin, Teilhard de Chardin and William Shakespeare. Attempts to define humanness upon a narrow range of criteria, as some have tried, is argued as flawed, for humanness is more elusive than a single or a few demonstrated phenomena. The path that Darwin pursued in determining the place of humans in nature in his book The Descent of Man, and Selection in Relation to Sex is assessed from a 19thcentury perspective; the difficulties he faced, both personally and with the broader public, are reviewed and then evaluated in a modern context. Darwin’s thesis adheres to scientific principles, and is debated, defended and later verified on these principles. This is somewhat at variance to the approach adopted by the priest-scientist de Chardin a century later in his major work, The Phenomenon of Man—in which an attempt is made to reconcile a deep Christian faith with science. De Chardin scores well from a theological viewpoint, but fails on scientific grounds as his thesis moves beyond the realms of empiricism into mysticism. Surprisingly, de Chardin’s predicament of a future wherein human evolution enters a new stage of consciousness through the noosphere (an invisible layer of thought encompassing the globe) has been partially realised through the worldwide web, although the nature of the web is almost certainly not what de Chardin might have anticipated, or desired. Science too fails to answer all, particularly the nature of God. Darwin considered the Creator in several of his works and does not dismiss the concept of a farseeing deity, although we are left with the notion that he died agnostic. Humanness is derived from an elevated moral code and this is reflected in our arts, particularly literature, wherein we may temporally reflect upon quintessential human traits such as mercy. However, expression of the arts is only achievable by the individual being part of a greater whole: the human community, the essence of which is distilled in the Bantu concept of ubuntu, wherein humanness is best realised through the act of living in harmony.
Editorial
Buckeridge Marcos S.
Brazilian Journal of Botany , 2003,
Abstract:
Growth, photosynthesis and stress indicators in young rosewood plants (Aniba rosaeodora Ducke) under different light intensities
Gon?alves, José Francisco de Carvalho;Barreto, Denize Caranhas de Sousa;Santos Junior, Ulysses Moreira dos;Fernandes, Andreia Varmes;Sampaio, Paulo de Tarso Barbosa;Buckeridge, Marcos Silveira;
Brazilian Journal of Plant Physiology , 2005, DOI: 10.1590/S1677-04202005000300007
Abstract: aniba rosaeodora is an amazonian tree species that belongs to the family lauraceae. due to intense exploitation for extraction of essential oils (mainly linalol), a. rosaeodora is now considered an endangered species. on the other hand, there is little information about its ecophysiology which would be useful to support future forest planting programs. hence, the effect of different light intensities on the growth and photosynthetic characteristics of young plants of a. rosaeodora was studied. nine-month-old plants were subjected to four light treatments (t1= 10 a 250 μmol.m-2.s-1 / control; t2=500 to 800, t3=700 to 1000 and t4=1300 to 1800 μmol.m-2.s-1 / full sunlight). allometric variables, gas exchange, contents of pigments and chlorophyll a fluorescence were analysed. as to the relative growth rates, it was found that plants of a. rosaeodora showed higher biomass accumulation when grown under intermediary irradiance conditions (t2). the best photosynthetic performance was achieved under conditions of t3. when growth was correlated with photosynthesis, it was found that plants under treatments t2 and t3 presented better responses in comparison with the lowest (t1) and highest (t4) light extremes. the highest pigment contents were obtained for plants in the shade (t1) and the lowest for those exposed to full sunlight (t4). the photochemical efficiency of photosystem ii (fv/fm) was found that only plants in the shade treatment (t1) presented no stress from high irradiance. these findings suggest that both treatments (t1 and t4) altered the function of the a. rosaeodora plants, inhibiting photosynthesis and growth. plants of a. rosaeodora developed photo-protection mechanisms under full sunlight. however, the species presented better photosynthetic response and biomass gain under intermediary irradiance conditions, displaying relative physiological plasticity, during the seedling phase.
Medical informatics in an undergraduate curriculum: a qualitative study
David L Buckeridge, Vivek Goel
BMC Medical Informatics and Decision Making , 2002, DOI: 10.1186/1472-6947-2-6
Abstract: We conducted a qualitative study to identify issues facing the introduction of medical informatics into an undergraduate medical curriculum. Nine key informants at the University of Toronto medical school were interviewed, and their responses were transcribed and analyzed to identify consistent themes.The field of medical informatics was not clearly understood by participants. There was, however, strong support for medical informatics education, and the benefits of such education were consistently identified. In the curriculum we examined, medical informatics education was delivered informally and inconsistently through mainly optional activities. Issues facing the introduction of medical informatics education included: an unclear understanding of the discipline; faculty and administrative detractors and, the dense nature of the existing undergraduate medical curriculum.The identified issues may present serious obstacles to the introduction of medical informatics education into an undergraduate medicine curriculum, and we present some possible strategies for addressing these issues.It is important that physicians be educated in medical informatics. Professional bodies [1,2], and commissions [3] support this position and make it clear that education must go beyond computer literacy to address the fundamentals of handling data, information, and knowledge. Educating physicians in medical informatics should enable many things, including appropriate interaction with clinical information systems, and the ability to utilize the Internet to inform themselves and their patients. In short, an education in medical informatics is essential for the many roles of a physician including clinician, educator, researcher, manager, and life-long learner [1].Without a basic education in medical informatics physicians are limited in their ability to make effective use of informatics methods and information technology. Moreover, without appropriate input from physicians skilled in medical
RESPUESTAS DE LAS PLANTAS ANTE LOS FACTORES AMBIENTALES DEL CAMBIO CLIMáTICO GLOBAL: REVISIóN
Yepes,Adriana; Buckeridge,Marcos Silveira;
Colombia Forestal , 2011,
Abstract: climate change is composed of a succession of meteorological processes that alter the performance of the natural systems, such as productivity, food sources, biodiversity and human activities. the natural ecosystems are essential for the global equilibrium, because they contain the bulk of the terrestrial carbon. plants are important carbon reservoirs, because of their ability to take co2 through photosynthesis and transform it into organic compounds such as cellulose (carbon sequestration). there is a growing interest to understand the global change process and its relationship with the carbon cycle with plant dynamics. elevated co2 concentration in the atmosphere increases leaf photosynthesis, but it is not known whether this enhancement will be maintained over time. in the present work, we review general aspects of climate change science, and some technologies applied to the study of elevated co2 concentrations effects in plants. also, physiological and metabolic responses associated to global change, such as high temperature and drought will be described. the inter disciplinarity related to the research associated to molecular biology, biochemistry, physiology, ecology and climatology, to name but a few, will afford the adoption of a more integrated approach of these events. this is crucial for the establishment of future strategies of governments and private companies to face the effects of the global climate changes.
Effect of abscisic acid on the mobilisation of galactomannan and embryo development of Sesbania virgata (Cav.) Pers. (Leguminosae - Faboideae)
POTOMATI, ADRIANA;BUCKERIDGE, MARCOS S.;
Brazilian Journal of Botany , 2002, DOI: 10.1590/S0100-84042002000300006
Abstract: galactomannans (gm) are storage cell wall polysaccharides present in endospermic seeds of legumes. they are thought to be storage polymers, since it has been observed for a few species (among them sesbania virgata) that they are completely broken down after germination and their products are transferred to the growing embryo. we examined the effect of 10-4 m abscisic acid (aba) on the degradation of galactomannan in isolated endosperms and intact seeds of s. virgata. we found that after seed germination the initial embryo growth was retarded. ultrastructural analysis showed that the embryo is completely surrounded by an endosperm which displays very thick galactomannan-containing cell walls. although an inhibitory effect has been observed on the increase of fresh mass of the embryo, the effect of aba on the dry mass was weaker and transitory (from 48 to 96 h). endosperm dry mass and galactomannan degradation were significantly inhibited and the activity of a-galactosidase was strongly affected. the addition of aba before and/or after the start of mobilisation in intact seeds or isolated endosperms, showed that whereas addition before mobilisation did not affect dry mass decrease in intact seeds, it was strongly affected in isolated endosperms. on the other hand, whereas it affected embryo fresh mass increase in intact seeds, but not in isolated embryos, no significant effect was observed on dry mass. these results suggest that aba affects galactomannan degradation and by doing so, prevents water absorption by the embryo, rather than affect its dry mass. as aba has been detected in the endosperm of seeds of s. virgata, it is proposed that it probably acts as a modulator of galactomannan mobilisation and consequently synchronises it with early growth of the embryo.
Effect of abscisic acid on the mobilisation of galactomannan and embryo development of Sesbania virgata (Cav.) Pers. (Leguminosae - Faboideae)
POTOMATI ADRIANA,BUCKERIDGE MARCOS S.
Brazilian Journal of Botany , 2002,
Abstract: Galactomannans (GM) are storage cell wall polysaccharides present in endospermic seeds of legumes. They are thought to be storage polymers, since it has been observed for a few species (among them Sesbania virgata) that they are completely broken down after germination and their products are transferred to the growing embryo. We examined the effect of 10-4 M abscisic acid (ABA) on the degradation of galactomannan in isolated endosperms and intact seeds of S. virgata. We found that after seed germination the initial embryo growth was retarded. Ultrastructural analysis showed that the embryo is completely surrounded by an endosperm which displays very thick galactomannan-containing cell walls. Although an inhibitory effect has been observed on the increase of fresh mass of the embryo, the effect of ABA on the dry mass was weaker and transitory (from 48 to 96 h). Endosperm dry mass and galactomannan degradation were significantly inhibited and the activity of alpha-galactosidase was strongly affected. The addition of ABA before and/or after the start of mobilisation in intact seeds or isolated endosperms, showed that whereas addition before mobilisation did not affect dry mass decrease in intact seeds, it was strongly affected in isolated endosperms. On the other hand, whereas it affected embryo fresh mass increase in intact seeds, but not in isolated embryos, no significant effect was observed on dry mass. These results suggest that ABA affects galactomannan degradation and by doing so, prevents water absorption by the embryo, rather than affect its dry mass. As ABA has been detected in the endosperm of seeds of S. virgata, it is proposed that it probably acts as a modulator of galactomannan mobilisation and consequently synchronises it with early growth of the embryo.
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