The effect of artificial shading on microclimate conditions in a soybean crop

Foi estudado o efeito do sombreamento artificial sobre a resistência estomática e as condições microclimáticas na cultura da soja (Glycine max (L.) Merrill). As telas plásticas usadas para regular o nível de radiação solar (30%, 50%, 70% e 100%) alteraram a qualidade da luz incidente sobre as plantas. No entanto, a temperatura e a umidade relativa do ar não foram modificadas, embora a temperatura da copa das plantas tenha decrescido com o sombreamento. As plantas sombreadas apresentaram maiores valores de resistência estomática que as plantas expostas a plena radiação solar.The effect of artificial shading was studied on stomatal resistance and microclimate conditions in a soybean crop (Glycine max (L.) Merrill.). The plastic screen used to regulate the solar radiation level (30%, 50%, 70% and 100% of sunlight) altered the quality of the incident light on soybean plants. White the air temperature and relative humidity were not modifield, the canopy temperature was reduced by shading. Shaded plants showed greater values of stomatal resistance than the plants under full sunlight

Growth and solar energy conversion in soybeans grown under four solar radiation levels

O crescimento e a conversão da energia solar em soja (Glicyne max (L.) Merr. cv. 'UFV'-2), sob quatro níveis de radiação solar incidente (30%, 50%, 70% e 100%), foram estudados em condições de campo. As colheitas de material foram realizadas em intervalos regulares de 14 dias. As taxas de crescimento da cultura decresceram com a redução da radiação solar, sendo as diferenças devidas a menores taxas assimilatórias líquidas e a menores índices de área foliar nas plantas sombreadas. A taxa assimilatória líquida e a taxa de crescimento relativo declinaram tanto com a ontogenia como com a redução da radiação solar. A razão de área foliar aumentou com sombreamento, devido principalmente às variações na área foliar específica, uma vez que a razão de peso foliar não apresentou alteração sensível. A eficiência de conversão da energia solar aumentou com o sombreamento e decresceu com a ontogenia das plantas. As eficiências máximas de conversão da energia solar foram 1,70 1,65%, 1,91% e 2,26% para 100%, 70%, 50% e 30% da luz solar incidente. Os valores da eficiência média de conversão da energia solar foram 0,33%, 0,48%, 0,45% e 0,59% em ordem decrescente de densidade do fluxo de luz.Growth and efficiency of solar energy conversion were studied in soybean (Glycine max (L.) Merrill) cv. UFV-2 grown under four levels (30%, 50%, 70% and 100%) of solar radiation incidence under field conditions. Plant samples were collected every 14 days regularly. Crop growth rates decreased with reduction of solar radiation, and these differences were due to reduced net assimilation rates and to smaller leaf areas presented by shaded plants. Net assimilation rate and relative growth rate declined with ontogeny as well as with reduction of solar radiation. The leaf area ration increased with shading, mainly due to variations in specific leaf area, because leaf weight ratio did not change significantly. The efficiency of solar energy conversion increased with shading and decreased with plant ontogeny. Maximum efflciencies of solar energy conversion were 1.70%, 1.65%, 1.91% and 2.26% for the 100%, 70%, 50% and 30% light treatments. The average efficiency of solar energy conversion throughout the entire crop cycle was of 0.33%, 0.48%, 0.45% and 0.59% for the decreasing light levels

Development and assimilate partitioning in Glycine max grown under four light flux densities

O desenvolvimento e a partição de assimilados foram estudados em soja Glycine max (L.) Merr. cv. 'UFV-2', submetida a quatro níveis de luz (30, 50, 70 e 100% da radiação solar incidente), em condições de campo. O número máximo de folhas e a altura máxima das plantas coincidiram com o início do enchimento de grãos em todos os níveis de luz. A redução da densidade do fluxo radiante produziu aumento na altura das plantas e redução no número de folhas e de vagens. O sombreamento alterou a partição de assimilados entre os diversos órgãos, mas não modificou a ordem sequencial dos drenos metabólicos preferenciais. As taxas de acúmulo de matéria seca em cada órgão foram tanto mais elevadas quanto maior o nível de luz incidente. As taxas de acúmulo de matéria seca das raízes foram mais afetadas pelo sombreamento do que as dos outros órgãos.Development and assimilate partitioning were studied in Glycine max (L.) Merr. cv. UFV-2 under tour light levels (30, 50, 70 and 100% of sunlight) in field conditions. Irrespective of light flux densities, the maximum number of leaves and maximum height of the plants were attained at the onset of grain filling. Stem elongation increased and the number of leaves and pods were reduced by decreasing light levels. Shading altered the assimilate partitioning among parts but did not change the sequential order of the preferential sinks. The dry matter rates of each organ increased as the light flux densities increased. The rates of root dry matter were more affected by shading than the rates of dry matter production of the other organs

Growth, dry matter production and productivity of soybean grown under four solar radiation levels

Foram estudados, em condições de campo, o crescimento, a produção de matéria seca e a produtividade da soja (Glycine max (L.) Merrill), sob quatro níveis de radiação solar incidente (30%. 50%, 70% e 100%). O crescimento apresentou três fases distintas: A inicial - da germinação à floração-, na qual o crescimento foi relativamente lento; a intermediária - entre a floração e o inicio do enchimento das sementes -, quando o crescimento foi acelerado; e a final - fase do desenvolvimento das sementes -, em que o crescimento voltou a ser muito lento, com tendência a atingir um patamar. O sombreamento reduziu o acúmulo de matéria seca na planta e nos seus órgãos. Os valores máximos da produção de matéria seca dos órgãos foram atingidos em torno do 92º dia para as folhas, 104º para as raízes, independentemente do nível de luz; no caule ao 103º dia a meia e plena radiação, e ao 108º dia após a emergência, nos níveis de 30% e 70% da luz incidente. Houve uma defasagem de dez a quinze dias entre os crescimentos máximos do caule e folha. A matéria seca acumulada nos pericarpos e sementes aumentou vigorosamente até a colheita final nos maiores níveis de luz, e de forma lenta nos menores níveis de radiação incidente. Houve uma correlação linear (R2 = 0,97) entre o rendimento de sementes e a biomassa. O sombreamento prolongou o período de acúmulo de matéria seca dos diversos órgãos, principalmente o período de maturação. A redução da radiação solar aumentou a razão parte aérea/sistema radicular, o acamamento de plantas e o aborto de flores e vagens. Já o índice de colheita não foi alterado pelos diferentes níveis de luz.Growth, dry matter production and productivity of soybean (Glycine max (L.) Merril), grown under field conditions al four light levels (30%, 50%, 70% and 100% of sunlight) were studied. Soybean growth presented three distinct phases: initial phase, from germination to flowering, in which growth was relatively slow, intermediate phase, between flowering and beginning of seed filling, when growth was accelerated; and, phase of seed development, when growth was very slow, with tendency of reaching a plateau. Shading reduced dry matter accumulation in the whole plant and its organs. Maximum dry weight productions of the organs were reached at the 92nd day for the leaves, at the 104th day for the roots, independently of light levels, at the 103rd day under half to full sunlight, and at the 108th day after emergence at 30% and 70% of sunlight for stens. There was a ten to fifteen-day difference between maximum stem and leaf growth. The dry matter accumulated in pericarps and seeds increased strongly until to final harvest in the highest light levels and slowly in the lowest light levels. There was a straight linear correlation (R² = 0.97) between yield and biomass. Shading extended the period of dry matter accumulation to all organs, meanly the maturation time. Solar radiation reduction increased shoot/root ratio, plant lodging and flower and pod drops. The harvest index was not modified by light levels

Efeito da densidade do fluxo radiante sobre a nodulação da soja

The effect of light flux density (30%, 50%, 70% and 100% of sunlight) on soybean (Glycine max (L.) Merrill cv. UFV-2) nodulation was studied under field conditions. Shade reduced the number, dry weight, growth rate of nodules, and also accelerated their senescence. Nodule number, dry weight and growth rate decayed quickly during pod filling, evidencing a competition for assimilate between seeds and nodules. Nitrogen content was shown to be related to light flux density.Estudou-se, em condições de campo, o efeito do nível da radiação solar incidente (30%, 50%, 70% e 100%) na nodulação da soja (Glycine max (L.) Merrill) cv. 'UFV-2'. O sombreamento reduziu o número médio, a matéria seca e a taxa de crescimento dos nódulos, e acelerou a senescência nodular. O número, a matéria seca e a taxa de crescimento dos nódulos declinaram rapidamente no período de enchimento das vagens, mostrando haver uma competição por assimilados entre as sementes e os nódulos. O conteúdo de nitrogênio foi positivamente relacionado com a densidade do fluxo da radiação solar

Developing autonomous learning in first year university students using perspectives from positive psychology

Autonomous learning is a commonly occurring learning outcome from university study, and it is argued that students require confidence in their own abilities to achieve this. Using approaches from positive psychology, this study aimed to develop confidence in first‐year university students to facilitate autonomous learning. Psychological character strengths were assessed in 214 students on day one at university. Two weeks later their top three strengths were given to them in study skills modules as part of a psycho‐educational intervention designed to increase their self‐efficacy and self‐esteem. The impact of the intervention was assessed against a control group of 40 students who had not received the intervention. The results suggested that students were more confident after the intervention, and that levels of autonomous learning increased significantly compared to the controls. Character strengths were found to be associated with self‐efficacy, self‐esteem and autonomous learning in ways that were theoretically meaningful

Geometry of Time and Dimensionality of Space

One of the most distinguished features of our algebraic geometrical, pencil concept of space-time is the fact that spatial dimensions and time stand, as far as their intrinsic structure is concerned, on completely different footings: the former being represented by pencils of lines, the latter by a pencil of conics. As a consequence, we argue that even at the classical (macroscopic) level there exists a much more intricate and profound coupling between space and time than that dictated by (general) relativity theory. It is surmised that this coupling can be furnished by so-called Cremona (or birational) transformations between two projective spaces of three dimensions, being fully embodied in the structure of configurations of their fundamental elements. We review properties of some of the simplest Cremona transformations and show that the corresponding "fundamental" space-times exhibit an intimate connection between the extrinsic geometry of time dimension and the dimensionality of space. Moreover, these Cremonian space-times seem to provide us with a promising conceptual basis for the possible reconciliation between two extreme concepts of (space-)time, viz. physical and psychological. Some speculative remarks in this respect are made

Short-term effects of marijuana smoking on cognitive behavior in experienced male users

The effects of smoking marijuana on the ability to use abstract concepts was tested in 12 experienced marijuana users. Each subject was tested three times, after smoking prepared 300 mg cigarettes containing either 0, 1.5 or 2.9% δ 9 -THC in different sessions according to a Latin Square design. The same number of whole and/or partial cigarettes was smoked by each subject in each of the three sessions. This was determined for individual subjects by the number of 2.9% δ 9 -THC marijuana cigarettes that the subject had been willing to smoke in a pre-experimental session up to a maximum of 1200 mg. The following tests of concept formation and usage were used: 1. a letter series test; 2. a word grouping test; 3. a conceptual clustering memory test; 4. a closure speed test; 5. Witkin's Embedded Figures Test; 6. a size weight illusion test; 7. Luchin's Water Jar Test; 8. Luchin's Hidden Word Test; and 9. an anagram test. Marijuana smoking led to a dose-related impairment on the letter series, word grouping, closure speed, and Embedded Figures test. Performance on the size-weight illusion, Luchin's Water Jar, Luchin's Hidden Word, and the anagram tests were unaffected. Conceptual clustering decreased after marijuana smoking. In most cases only the differences between 0 and 2.9% δ 9 -THC marijuana were statistically significant.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46387/1/213_2004_Article_BF00429295.pd