973 resultados para B ... n C ... f.


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广1211 1.13Siganus vermiculatusS. punctatissimusSiganus unimaculatus112740 2. 齿 3a.11b.9c.5921 4. Nelson1994Siganus Forsskål, 1775Siganus Forsskål, 1775 Lo Seale, 1906(Woodland, 1990; 2001

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Dilution experiments were performed to examine the growth rate and grazing mortality rate of size-fractionated phytoplankton at three typical stations, inside and outside the bay, in the spring and summer of 2003 in the Jiaozhou Bay, China. in spring, the phytoplankton community structure was similar among the three stations, and was mainly composed of nanophytoplankton, such as, Skeletonema costatum and Cylindrotheca closterium. The structure became significantly different for the three stations in summer, when the dominant species at Stas A, B and C were Chaetoceros curvisetus, Pseudo-nitzschia delicatissima, C. affinis, C. debilis, Coscinodiscus oculus-iridis and Paralia sulcata respectively. Tintinnopsis beroidea and T. tsingtaoensis were the dominant species in spring, whereas the microzooplankton was apparently dominated by Strombidium sp. in summer. Pico- and nanophytoplankton had a relatively greater growth rate than microzooplankton both in spring and summer. The growth rate and grazing mortality rate were 0.18 similar to 0.44 and 0.12 similar to 1.47 d(-1) for the total phytoplankton and 0.20 similar to 0.55 and 0.21 similar to 0.37 d-1 for nanophytoplankton in spring respectively. In summer, the growth rate and grazing mortality rate were 0.38 similar to 0.71 and 0.27 similar to 0.60 d-1 for the total phytoplankton and 0.11 similar to 1.18 and 0.41 similar to 0.72 d(-1) for nano- and microphytoplankton respectively. The carbon flux consumed by microzooplankton per day was 7.68 similar to 39.81 mg/m(3) in spring and 12.03 similar to 138.22 mg/m(3) in summer respectively. Microzooplankton ingested 17.56%similar to 92.19% of the phytoplankton standing stocks and 31.77%similar to 467.88% of the potential primary productivity in spring; in contrast, they ingested 34.60%similar to 83.04% of the phytoplankton standing stocks and 71.28%similar to 98.80% of the potential primary productivity in summer. Pico- and nanophytoplankton appeared to have relatively greater rates of growth and grazing mortality than microphytoplankton during the experimental period. The grazing rate of microzooplankton in summer was a little bit greater than that in spring because of the relatively higher incubation temperature and different dominant microzooplankton species. Microzooplankton preferred ingesting nanophytoplankton to microphytoplankton in spring, while they preferred ingesting picophytoplankton to nanophytoplankton and microphytoplankton in summer. Compared with the results of dilution experiments performed in various waters worldwide, the results are in the middle range.

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The area of the southwestern Nansha Trough is one of the most productive areas of the southern South China Sea. It is a typical semi-deep sea area of transition from shoal to abyssal zone. To understand distributions and roles of nitrogen forms involved in biogeochemical cycling in this area, contents of nitrogen in four extractable forms: nitrogen in ion exchangeable form (IEF-N), nitrogen in weak acid extractable form (WAEF-N), nitrogen in strong alkali extractable form (SAEF-N) and nitrogen in strong oxidation extractable form (SOEF-N), as well as in total nitrogen content (TN) in surface sediments were determined from samples collected from the cruise in April-May 1999. The study area was divided into three regions (A, B and C) in terms of clay sediment (< 4 mu m) content at < 40%, 40%-60% and > 60%, respectively. Generally, region C was the richest in the nitrogen of all forms and region A the poorest, indicating that the finer the grain size is, the richer the contents of various nitrogen are. The burial efficiency of total nitrogen in surface sediments was 28.79%, indicating that more than 70% of nitrogen had been released and participated in biogeochemical recycling through sediment-water interface.

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,.Juniperus przewalskii Kom.20392trnT-trnF;3(haplotype),:HapA,HapAHapBHapC.HT=0.511,GST=0.847.,Hap AHap BHap C,,..Hap A,.,.

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The combined occurrence of both herkogamy and dichogamy in a hermaphrodite species has been considered to strongly favour outcrossing. In this study, we investigated in detail the reproductive ecology of Gentiana straminea Maxim. (Gentianaceae), a hermaphrodite perennial endemic to the Qinghai-Tibet Plateau. In a series of observations and experiments over four consecutive years, we examined whether the combination of dichogamy and herkogamy in individual flowers completely prevents geitonogamous pollen transfer in this species. The mode of floral development clearly indicates that autonomous self-pollination is completely avoided through herkogamy and dichogamy in individual flowers. This implication was confirmed by the breeding experiments, since no seed was produced when flowers were isolated. However, this gentian proved to be highly self-compatible when geitonogamous selfing was artificially induced. Many flowers opened simultaneously on individual plants, the ratio of male to female phase flowers was close to 2:1 in each inflorescence, at the full anthesis phase, and they were randomly distributed amongst the upper, middle and lower parts of each stem's inflorescence. On average, Bombus sushikini Skorikov, the most frequent visitor and only legitimate pollinator of G. straminea, visited nearly two flowers per inflorescence, and four flowers per plant. Among the pollinators' foraging bouts, the proportions of geitonogamous visits to inflorescences or flowers within an individual plant were 29% and 37%, respectively. Therefore, despite the strict dichogamous and herkogamous characteristics of the individual flowers, geitonogamous selfing might still prevail in G. straininea because of the size of its floral displays and the continuous visiting behavior of B. sushkini. (C) 2005 Elsevier SAS. All rights reserved.

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In the alpine region of the Tibetan Plateau, five perennial grass cultivars, Bromus inermis (B), Elymus nutans (E), Clinelymus nutans (C), Agropyron cristatum (A), and Poa crymophila (P) were combined into nine communities with different compositions and ratios, B+C, E+A, B+E+A, E+B+C,C+E+A,B+E+C+A,B+C+A+P,B+E+A+P and E+C+A+P. Each combination was sown in six 10 X 10 m plots with three hand-weeded plots and three natural-growing plots in a completely randomised design in 1998. A field experiment studied the performance of these perennial grass combinations under the competitive interference of annual weeds in 3 consecutive years from 1998 to 2000. The results showed that annual weeds occupied more space and suppressed the growth of the grasses due to earlier germination and quicker growth in the establishment year, but this pattern changed in the second and third years. Leaf area indexes (LAIs) of grasses were greatly decreased by the competitive interference of weeds, and the negative effect of weeds on LAIs of grasses declined and stabilised in the second and third years. E+B+C, B+E+C+A, and B+E+A+P possessed relatively higher LAIs (P < 0.05) among all grass combinations and their LAIs were close to five when the competitive interference of weeds was removed. Grasses were competitively inferior to weeds in the establishment year, although their competitive ability (aggressivities) increased throughout the growing season. In the second and third years, grasses were competitively superior to weeds, and their competitive ability decreased from May until August and increased in September. Dry matter (DM) yields of grasses were reduced by 29.8-74.1% in the establishment year, 11.0-64.9% in the second year, and 16.0-55.8% in the third year by the competitive interference of weeds. B+E+C+A and B+E+A+P can produce around 14 t/ha of DM yields, significantly higher (P < 0.05) than the production of the other grass combinations in the second and third years after the competitive interference of weeds was removed. It was preliminarily concluded that removal of competitive interference of weeds increased the LAIs of all grass swards and improved the light interception of grasses, thus promoting the production of perennial grass pastures. The germination stage of the grasses in the establishment year was the critical period for weeding and suppression of weeds should occur at an early stage of plant growth. The grass combinations of B+E+C+A and B+E+A+P were productive and can be extensively established in the alpine regions of the Tibetan Plateau. Two or three growing seasons will be needed before determining success of establishment of grass mixtures under the alpine conditions of the Tibetan Plateau.

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Pollen morphology of 40 species of Rheum, belonging to eight sections, was investigated under LM and SEM. Four new exine patterns were found in the species: a) microcchinate-foveolate, b) rugulate, c) verrucate-perforate, and d) verrucaterugulate ornamentation. In addition, two patterns, the Rheum-type pollens with microechinate-perforate and fine-reticulate, as previously described, were also confirmed in the present study. Based on above study the evolution trends of pollen morphology in the taxa involved were discussed phylogenetically as below. As microechinate-perforate exine pattern existed commonly, the pattern is, therefore, regarded as the most primitive among all the six types. The fine-reticulate type was thought as a derivative type, deriving from the basic micro echinate-foveolate-perforate pattern, and followed by the rugulate and verrucate-perforate ornamentation. The verrucate-rugulate ornamentation should be the most advanced. More than one pollen type often exist in most of the sections in Rheum. The pollen morphology of Rheum was strongly correlated with its geographical and ecological distribution. Three medicinally important species R. officinale, R. palmation and R. tanguticum can be palynologically distinguished by their ornamentations.

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TM123aTMbTMcTMde

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A prodão de sementes de forrageiras tropicais representa um importante segmento da indústria de sementes no Brasil e há a necessidade do estabelecimento de prioridades para aumentar a eficincia do setor. Neste documento esto apresentados os resultados da discuso efetuada pelo grupo de trabalho reunido durante o Workshop "Tecnologia de Sementes de Forrageiras Tropicais: Demandas Estratégicas de Pesquisa", realizado pela Embrapa Gado de Corte em abril de 2008. As demandas de pesquisa discutidas e consideradas prioririas foram pertinentes a vrios aspectos da produão e tecnologia de sementes de forrageiras tropicais, da semeadura ao processamento, bem como ao armazenamento e anlises laboratoriais.

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Touros jovens da ra Nelore (n=6) foram mantidos em pasto formado de Brachiaria brizantha desde a desmama em dietas com diferentes nveis de zinco. Foram formados aleatoriamente dois grupos que receberam diariamente, durante dois anos, diferentes concentraçes de zinco no sal mineral: T1 (n=4), os animais não receberam suplemento com zinco e T2 (n=2), 60 mg/kg/dia de Zn inorgnico suplementar. A concentraço de Zn na pastagem variou de 17,8 guas) a 12,8 mg/kg (seca), respectivamente. A partir dos 14 meses de idade, os animais foram submetidos quinzenalmente a exame de smen e colheita de sangue. A morfologia espertica foi estimada, incluindo a mensuraão da cabeça espertica a partir de esfregaços coradas pelo todo de Fuelgen, em imagens captadas digitalmente e processadas pelo software Kontron Eletronik Imaging System, KS 400-2.0. A concentraço de zinco no plasma foi dosada por spectrofotometria de absorço atmica. Os resultados mostraram que os touros do T1 tiveram qualidade seminal inferior (P<0,05) em relaço ao T2. Observou-se variaço das características seminais em funço da data da colheita, evidenciando efeito estacional sobre a qualidade do men. Os defeitos mais encontrados foram de peça intermedria e cauda. A concentraço de Zinco (Zn) na circulaço sanínea foi maior (P<0,01) no T1 em comparaão ao T2 (0,72 0,01 x 0,66 ±0,01, respectivamente). A rea da cabeça espertica de espermatozóides morfologicamente normais e com defeitos de cabeça, pa intermediria e cauda foi maior (P<0,01) para os touros do T1 em relaço aos do T2. Ademais, espermatozóides com fragmentaão nuclear apresentaram forma mais alongada quando comparados àqueles sem alteraões morfológicas. As correlões encontradas sugerem a importância do Zn na qualidade seminal, especialmente pelos efeitos deletrios que sua deficincia (subclnica) causa na morfologia espermática.

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A prodão de sementes de forrageiras tropicais representa um importante segmento da indústria de sementes no Brasil e há a necessidade do estabelecimento de prioridades para aumentar a eficincia do setor. Neste documento esto apresentados os resultados da discuso efetuada pelo grupo de trabalho reunido durante o Workshop "Tecnologia de Sementes de Forrageiras Tropicais: Demandas Estratégicas de Pesquisa", realizado pela Embrapa Gado de Corte em abril de 2008. As demandas de pesquisa discutidas e consideradas prioririas foram pertinentes a vrios aspectos da produão e tecnologia de sementes de forrageiras tropicais, da semeadura ao processamento, bem como ao armazenamento e anlises laboratoriais.

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O tomateiro (Solanum lycopersicum L. = Lycopersicon esculentum Mill.) é uma das plantas oleráceas mais cultivadas no Brasil e o seu fruto, o tomate, é uma das olecolas mais consumidas na mesa do brasileiro e muito usado pela agroindústria. Uma das doenças do tomateiro mais temidas pelos produtores é a requeima, causada pelo fungo Phytophtora infestans, que provoca grande destruião na cultura em pouco tempo. Este trabalho teve o objetivo de caracterizar isolados de P. infestans, coletados de tomateiros, quanto ao grupo de compatibilidade, viruncia e à resisncia ao fungicida mefenoxan. Vinte e seis isolados foram caracterizados quanto ao grupo de compatibilidade; 24 foram caracterizados quanto à resisncia ao mefenoxan; e determinou-se o espectro de virulência de 14 isolados. Todos os 26 isolados testados foram classificados como do grupo A1 de compatibilidade. Em relaço à virulncia, todos os isolados foram virulentos à cultivar de tomate 'IPA-5'. A maioria foi virulenta em plantas de tomate com os genes Ph1 (92,86%) ou Ph2 (78,57%) e uma pequena parte dos isolados foram virulentos em plantas com o gene Ph3 (21,43%). Quanto à resisncia ao mefenoxan, a freência de isolados sensveis, intermedrios e resistentes foram de 16,67%, 16,67% e 66,66%, respectivamente. H evidências da não-reproduão sexuada e formaão de oósporos nos campos de tomate do pas, retardando o aparecimento da doea. Devido a um maior mero de isolados resistentes ao mefenoxan, o controle da requeima com este fungicida pode ser ineficiente em campo. Uma vez que o pageno apresentou um amplo espectro de virulência, a utilizaão de cultivares com resistncia vertical a requeima não é recomendada. O manejo integrado da requeima é a forma mais eficaz de se controlar a doença.

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2009