Microtextural characteristics of quartz grains transported and deposited by tsunamis and storms

International audienc

High resolution geochemical and grain-size analysis of the AD 1755 tsunami deposit: Insights into the inland extent and inundation phases

In the study of palaeotsunamis it is crucial to decipher the sedimentological record, to derive intensity of pastevents and to infer different inundation phases. To achieve this goal, it is important to apply high-resolutiontechniques that allow magnifying intra-deposit details (at a sub-centimetric scale) that otherwise would not beperceived; consequently, valuable information could be overlooked.In this work, we applied successfully high-resolution geochemical and grain-size analyses – XRF core-scanningand image analysis, respectively – to the AD 1755 tsunami deposit. This quartz sand enriched in bioclastdeposit (exhibiting high Si/Al and Ca/Ti) was recognized in the coastal stratigraphic sequence of Salgadoslagoon due to its contrasting composition when compared with the under and overlying mud layers with scarcebioclasts (exhibiting low Si/Al and Ca/Ti). In the absence of textural evidence, the identification of peakingconcentrations of Cl, S and Br (all major constituents of sea salt) in a continuous muddy sequence allowedslightly extending farther inland the limit of inundation. In addition, grain-size analysis data attested the fininginland of the deposit. Furthermore, despite the macroscopic massive structure of the tsunami deposit, throughoutthe lagoon, grain-size results revealed more complexity and allowed inferring up to four depositional sequencesdirectly associated with the AD 1755 tsunami inundation

Aeolian microtextures in silica spheres induced in a wind tunnel experiment: Comparison with aeolian quartz

Microtextures in quartz attributed to aeolian transport, principally bulbous edges and abrasion fatigue have seldom been tested in the laboratory under controlled conditions. A wind tunnel experiment was conducted, using glass spheres (>70% SiO2) as a proxy for quartz, with the objective of determining the extent of mechanical damage to silica/glass transported in a mixture with quartz beach sand. The microspheres were microscopically imaged prior to transport in a wind tunnel, subjected at velocities ranging from 4 to 13 m/s in sequential runs of 10 min. The range in velocity is capable of lifting grains into the air column or saltating quartz grains and silica/glass spheres to produce mechanical impact, i.e. abrasion commonly experienced in aeolian transport. With increasing velocity silica/glass spheres, which displayed minor imperfections prior to transport, began to show significant grain damage exhibiting increasing depth into the silica/glass fabric – a result of mechanical contact – as well as increasing frequency of craters, dislodged plates and abrasion fatigue. While pits appear earlier in the experiment (8 m/s), dislodged plates and abrasion fatigue need a threshold velocity of near 10 m/s to become more frequent. Bulbous edges on the grain surface, often considered the hallmark of aeolian transport, are not seen in the grain population analyzed, possibly because of the initial near-perfect sphericity of the silica/glass spheres. The experiment proved that aeolian transport throughout short distances and during a relatively short period of time is enough to imprint significant abrasion marks in microspheres. In fact, the microtextures produced were fresh surfaces, fractures and abrasion that imprinted areas of different sizes. A comparison of microtextural imprints on silica/glass spheres relative to coastal dune sands was made to better understand energy thresholds required to achieve grain damage

Anatomia foliar de soja infectada por Phakopsora pachyrhizi H. Sydow & Sydow e tratadas com extratos vegetais Leaf anatomy of soybean infected with Phakopsora pachyrhizi H. Sydow & Sydow and treated with plant extracts

Folhas de Glycine max (L.) Merril,infectadas pelo fungo Phakopsora pachyrhizi H. Sydow & Sydow e tratadas com extratos vegetais foram avaliadas, visando determinar in vivo as modificações anatômicas nas diferentes estruturas/tecidos foliares, além de reconhecer prováveis mecanismos de defesa. Folhas de soja cultivar 181 provenientes do quinto nó foram inoculadas com fungo e tratadas com diferentes extratos vegetais, água e álcool 70%. Para comparação foram analisadas a anatomia das folhas sadia e infectada e realizadas medidas nas estruturas/tecidos foliares. Na folha infectada, observou-se destruição da epiderme e parênquima lacunoso, visível proliferação de tricomas e cutícula espessada, principalmente na face abaxial. Observou-se a presença de compostos fenólicos nas células da epiderme quando rompida, em função do crescimento micelial. Nas folhas infectadas e tratadas com os extratos vegetais de Azadirachta indica, Maytenus ilicifolia e Allium sativum, as estruturas/tecidos vegetais apresentaram aumento de espessura por alongamento celular.<br>Glycine max (L.) Merril leaves, infected by the fungus Phakopsora pachyrhizi H. Sydow & Sydow and treated with plant extracts, were evaluated with the aim of determining in vivo the anatomical modifications in different leaf structures and of identifying probable defense mechanisms. Leaves from the 181 soybean cultivar originated from the fifth node were inoculated with the fungus and treated with different plant extracts, water and alcohol at 70%. For comparison, the anatomy of the healthy and infected leaves was analyzed and the leaf structures were measured. In the infected leaf, there was destruction of the epidermis and lacunar parenchyma, apparent trichome proliferation and denser cuticle, especially on the abaxial surface. There were also phenolic compounds in ruptured epidermis cells, due to mycelium growth. In the infected leaves treated with Azadirachta indica, Maytenus ilicifolia and Allium sativum extracts, the plant tissues had an increase in thickness due to cell elongation

Cultivares, espaçamento entrelinhas e programas de aplicação de fungicidas no controle de Phakopsora pachyrhizi Sidow em soja Cultivars, row spacing and fungicide application programs on Phakopsora pachyrhizi Sydow control in soybean

Com este trabalho, buscou-se avaliar a resposta de cultivares de soja, em duas safras, submetidas a diferentes espaçamentos entrelinhas e programas de controle sob pressão natural de Phakopsora pachyrhizi Sidow. Nas safras 07/08 e 08/09, os espaçamentos entrelinhas de 40, 50 e 60cm representavam as parcelas principais, as cultivares 'A 8000 RG' e 'A 6001 RG', as subparcelas e os programas de controle, as subsubparcelas. A redução do espaçamento entrelinhas permitiu melhores condições para o estabelecimento e progresso da ferrugem asiática para as duas cultivares e menor eficácia de controle. A melhor resposta de controle foi verificada com a utilização do programa após uma aplicação no estádio de desenvolvimento R1 e uma segunda aplicação 25 dias após a primeira. O espaçamento de 60cm entrelinhas proporcionou menores valores de doença acumulada e maior produtividade.<br>This study aimed to assess in two seasons, the response of soybean cultivars subjected to different row spacings and control programs under Phakopsora pachyrhizi Sidow natural pressure. The research was carried out at the seasons 07/08 and 08/09. The main plots were composed of the row spacings of 40, 50 and 60cm and the split plots corresponded to the cultivars A 8000 RG and A 6001 RG. The control programs were the split split plots.The reduction of row spacing allowed more conditions for the rust establishment and progress for both cultivars and less effective control. The best control response was verified using the program with an application in R1 and a second application, 25 days after the first one. The row spacing of 60cm gave lower AUDPC values and higher productivity