Seasonal changes in berry fluorescence induced by different levels of uv-radiation

Plant stress is usually diagnosed via physiological measurements on leaves such as water potential, photosynthetic rate or chlorophyll fluorescence. Since stress in the case of grapevines is of concern with respect to the quality of the fruit, we attempted to use one of the above mentioned techniques, chlorophyll fluorescence, directly on the fruit itself in order to investigate stress responses in vivo. Berry fluorescence was measured in an experiment with different levels of UV-B and UV-A radiation in the field in 2000 in Geisenheim with the variety Riesling. UV radiation has been shown to affect chlorophyll and was thus likely to show differences in fluorescence signals. Berry fluorescence was measured periodically between veraison and harvest on darkadapted berries (20min). For each berry, a light response curve was recorded followed by a recovery phase in the dark. The maximum quantum yield of PSII (qY) was determined after a saturation pulse at each light intensity. The qY decreased exponentially with increasing light intensity. The response level of the quantum yield of PSII decreased during ripening indicating a loss in chlorophyll and/or PSII capacity for all treatments. Effects of the different levels of UV-radiation on the light curve were only detected at the end of the ripening period, with higher quantum yield values recorded for the treatments protected against UV-A and UV-A+UV-B. Similar results were obtained after recovery in the dark. Changes in fluorescence signals were accompanied by a visual change in berry colour indicating changes in skin pigmentation, which may also have some effect on fruit qualityinfo:eu-repo/semantics/publishedVersio

Validation of an empirical model for grapevine leaf area estimation with data from simplified pruning systems

The performance of a mathematical model developed for non-destructive estimation of primary leaf area per shoot of Tempranillo grapevines, was tested using independent datasets from two vineyards with simplified pruning techniques. The first dataset was collected in Portugal on Cabernet Sauvignon grapevines subjected to mechanical hedge pruning and the second one in Germany on minimal pruned Riesling grapevines. For both datasets the model presented a very good fit between observed and estimated values with the error increasing with the increase in leaf area per shoot. The mean absolute percent error for all systems was lower or equal to 10% with lower absolute values (7.7%) for the Riesling dataset. Both linear regression between observed (dependent variable) and estimated (independent variable) leaf area had high and significant R2 with an intercept not significantly different from zero. Fitted lines were not significantly different from 1 for Cabernet Sauvignon, but slightly yet significantly different from 1 for Riesling fitted line (1.03), indicating that the model underestimated the leaf area per shoot. The good results obtained with this validation test show that the model can be used to accurately predict primary leaf area per shoot independent of variety, training system and climatic conditionsinfo:eu-repo/semantics/publishedVersio

Water in a warmer world – is atmospheric evaporative demand changing in viticultural areas?

The predicted developments in climate are region-specific and adaptation can only be successful considering the regional characteristics with its diverse technical, environmental, economic and social implications. One of the key concerns for many regions is the availability of water through precipitation, the distribution of precipitation throughout the year, and possible changes in evaporative demand of the atmosphere and thus water use. From rising temperatures it is mostly assumed that water holding capacity of the atmosphere will increase in the future as a function of the Clausius-Clapeyron law, which predicts an increase in the saturation vapour pressure of the atmosphere of 6–7% per degree Celsius. As a consequence, a simultaneous increase in potential evapotranspiration (ETp, the amount of water that could potentially be evaporated from soils and transpired by plants due to changes in climatic factors such as temperature, vapour pressure deficit, radiation and wind speed) is assumed in many cases, which would alter soil and plant water relations. However, the same underlying principles also predict an increase in precipitation by 1–2% per degree warming. Additionally, model predictions for many regions forecast altered precipitation patterns and thus in combination with the possibility of increased ETp, farmers around the world fear an increase in the likelyhood of water deficit and a reduction in the availability of water for irrigation. Contrary to expectations, there have been reports on a reduction in evaporative demand worldwide despite increasing temperatures. In many cases this has been related to a decrease in solar radiation observed for many areas on earth including wine growing regions in Europe until the beginning of the 80th (global dimming) of the last century. However, since then, solar radiation has increased again, but ETp did not always follow and a worldwide decrease in wind speed and pan evaporation has been observed. In order to evaluate different grape growing regions with respect to observed changes on precipitation patterns and ETp, the data of seven wine-growing areas in five countries in the Northern and Southern hemisphere across a large climatic trans-sect were analyzed (Rheingau, Germany, Burgundy, Rhone Valley, France, Napa Valley, USA, Adelaide Hills, Tasmania, Australia, Marlborough, New Zealand) were analyzed. Precipitation patterns differed vastly between locations and showed very different trends over observation periods ranging from 23 to 60 years. The ETp has increased continuously in only two of the seven wine growing areas (Rheingau and Marlborough). In most other areas, ETp has been stable during winter and summer for at least 22 years (Rhone Valley, Napa Valley, Tasmania), sometimes much longer (45 years Adelaide Hills), and has been declining in Burgundy after a period of strong increase for the last 13 years. The potential underlying factors are discussed in relation to observed shifts in precipitation patterns

Influence de différents niveaux de rayonnement UV sur la physiologie, le taux de pigments et la composition des baies, cépage Riesling

Changes in the stratospheric ozone concentration causes UV-radiation to increase. The response to UV-B radiation on the organ and cellular level is mainly an increase in the formation of UV-absorbing compounds meant to decrease UV-radiation penetration into the tissue. Some key enzymes involved in flavonoid biosynthesis and the phenyl-propanoid pathway have been shown to be up-regulated by UV-radiation, as are levels of key antioxidants glutathione and ascorbate, whereas carotenoid pigment formation and the incorporation of nitrogen into amino acids can be inhibited. Since components such as flavonoids, amino acids and carotenoids are important constituents of grapes with a marked effect on flavour development, some influence of altered UV-radiation can be expected. We investigated these possible effects under field conditions by selectively attenuating various portions of the light spectrum in the UV-part with polyester and di- and tri-acetate films and exposing the entire canopy or parts thereof to these conditions during berry development. We evaluated skin pigment composition using a non-destructive spectro-photometric technique. There was a strong UV-induced shift towards the formation of red and brown pigment components without affecting sugar levels. Chlorophyll degradation in the berry skin proceeded faster in the high UV-radiation treatments and this could be assessed for non-destructively by measuring berry fluorescence. Amino acid concentration was reduced under high levels of UV-B radiation and both the total bound glycosidic secondary metabolites and phenolics were increased. There were some effects noticeable on fermentation velocity and the retention of free and bound aromatic components in the wineinfo:eu-repo/semantics/publishedVersio

High-Intensity and High-Brightness Source of Moderated Positrons Using a Brilliant gamma Beam

Presently large efforts are conducted towards the development of highly brilliant gamma beams via Compton back scattering of photons from a high-brilliance electron beam, either on the basis of a normal-conducting electron linac or a (superconducting) Energy Recovery Linac (ERL). Particularly ERL's provide an extremely brilliant electron beam, thus enabling to generate highest-quality gamma beams. A 2.5 MeV gamma beam with an envisaged intensity of 10^15 s^-1, as ultimately envisaged for an ERL-based gamma-beam facility, narrow band width (10^-3), and extremely low emittance (10^-4 mm^2 mrad^2) offers the possibility to produce a high-intensity bright polarized positron beam. Pair production in a face-on irradiated W converter foil (200 micron thick, 10 mm long) would lead to the emission of 2 x 10^13 (fast) positrons per second, which is four orders of magnitude higher compared to strong radioactive ^22Na sources conventionally used in the laboratory.Using a stack of converter foils and subsequent positron moderation, a high-intensity low-energy beam of moderated positrons can be produced. Two different source setups are presented: a high-brightness positron beam with a diameter as low as 0.2 mm, and a high-intensity beam of 3 x 10^11 moderated positrons per second. Hence, profiting from an improved moderation efficiency, the envisaged positron intensity would exceed that of present high-intensity positron sources by a factor of 100.Comment: 9 pages, 3 figure

The metallic state in disordered quasi-one-dimensional conductors

The unusual metallic state in conjugated polymers and single-walled carbon nanotubes is studied by dielectric spectroscopy (8--600 GHz). We have found an intriguing correlation between scattering time and plasma frequency. This relation excludes percolation models of the metallic state. Instead, the carrier dynamics can be understood in terms of the low density of delocalized states around the Fermi level, which arises from the competion between disorder-induced localization and interchain-interactions-induced delocalization.Comment: 4 pages including 4 figure

Concentration Dependence of Superconductivity and Order-Disorder Transition in the Hexagonal Rubidium Tungsten Bronze RbxWO3. Interfacial and bulk properties

We revisited the problem of the stability of the superconducting state in RbxWO3 and identified the main causes of the contradictory data previously published. We have shown that the ordering of the Rb vacancies in the nonstoichiometric compounds have a major detrimental effect on the superconducting temperature Tc.The order-disorder transition is first order only near x = 0.25, where it cannot be quenched effectively and Tc is reduced below 1K. We found that the high Tc's which were sometimes deduced from resistivity measurements, and attributed to compounds with .25 < x < .30, are to be ascribed to interfacial superconductivity which generates spectacular non-linear effects. We also clarified the effect of acid etching and set more precisely the low-rubidium-content boundary of the hexagonal phase.This work makes clear that Tc would increase continuously (from 2 K to 5.5 K) as we approach this boundary (x = 0.20), if no ordering would take place - as its is approximately the case in CsxWO3. This behaviour is reminiscent of the tetragonal tungsten bronze NaxWO3 and asks the same question : what mechanism is responsible for this large increase of Tc despite the considerable associated reduction of the electron density of state ? By reviewing the other available data on these bronzes we conclude that the theoretical models which are able to answer this question are probably those where the instability of the lattice plays a major role and, particularly, the model which call upon local structural excitations (LSE), associated with the missing alkali atoms.Comment: To be published in Physical Review

Physiological responses and production of 'Syrah' vines as a function of training systems

Plant architecture and its interaction with agricultural practices and environmental constraints is determinant for grapevine canopy structure, which is related to carbon assimilation, bud fertility and fruit quality. In this context, this study evaluated the performance of field-grown 'Syrah' grapevines conducted by two management systems: Vertical Shoot Position (VSP) or a modified Geneva Double Curtain (GDC), in Pirapora, state of Minas Gerais, Brazil, during the winters of 2007 and 2008. The evaluations of leaf area, water relations and net CO2 assimilation were made at the end of the ripening period. Yield per vine and per hectare were estimated and mean berry weight and diameter, total soluble solids, pH and titratable acidity were evaluated during berry ripening. The grapevines trained in VSP had higher water status as compared to GDC, shown by differences in pre-dawn leaf water potential (&#968;pd) and stem water potential (&#968;stem). However, the CO2 assimilation was similar in both training systems. Fruit exposure was higher in VSP than in GDC, which contributed to increasing berry temperature. At harvest, the berries in GDC reached values near to 23 ºBrix whereas berries in VSP showed values near 21 ºBrix

Comprehensive analysis of epigenetic clocks reveals associations between disproportionate biological ageing and hippocampal volume

The concept of age acceleration, the difference between biological age and chronological age, is of growing interest, particularly with respect to age-related disorders, such as Alzheimer’s Disease (AD). Whilst studies have reported associations with AD risk and related phenotypes, there remains a lack of consensus on these associations. Here we aimed to comprehensively investigate the relationship between five recognised measures of age acceleration, based on DNA methylation patterns (DNAm age), and cross-sectional and longitudinal cognition and AD-related neuroimaging phenotypes (volumetric MRI and Amyloid-β PET) in the Australian Imaging, Biomarkers and Lifestyle (AIBL) and the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Significant associations were observed between age acceleration using the Hannum epigenetic clock and cross-sectional hippocampal volume in AIBL and replicated in ADNI. In AIBL, several other findings were observed cross-sectionally, including a significant association between hippocampal volume and the Hannum and Phenoage epigenetic clocks. Further, significant associations were also observed between hippocampal volume and the Zhang and Phenoage epigenetic clocks within Amyloid-β positive individuals. However, these were not validated within the ADNI cohort. No associations between age acceleration and other Alzheimer’s disease-related phenotypes, including measures of cognition or brain Amyloid-β burden, were observed, and there was no association with longitudinal change in any phenotype. This study presents a link between age acceleration, as determined using DNA methylation, and hippocampal volume that was statistically significant across two highly characterised cohorts. The results presented in this study contribute to a growing literature that supports the role of epigenetic modifications in ageing and AD-related phenotypes

Fotossíntese, relações hídricas e crescimento de cafeeiros jovens em relação à disponibilidade de fósforo

O objetivo deste trabalho foi avaliar de que maneira a alta disponibilidade de fósforo no solo afeta a fotossíntese e o crescimento de mudas de cafeeiro arábica (Coffea arabica). Mudas da cultivar Ouro Verde com aproximadamente quatro meses de idade, cultivadas com boa disponibilidade hídrica, foram submetidas a três tratamentos quanto à disponibilidade de fósforo: quantidade recomendada de P, na literatura (PA); duas vezes a dosagem utilizada em PA (P+); e sem adição de P ao solo (P-). Após 70 dias da aplicação dos tratamentos, foram avaliados: as trocas gasosas, a atividade fotoquímica, o potencial de água da folha, a condutância hidráulica da planta (K L), a partição de matéria seca na planta, os teores de pigmentos e carboidratos, e a composição química das folhas. O tratamento P- influenciou negativamente a fotossíntese, e levou à restrição do crescimento das plantas. As plantas do tratamento P+ apresentaram maior teor foliar de P (~1,9 g kg-1), com incrementos na assimilação de CO2, na eficiência instantânea de carboxilação e na atividade fotoquímica - maior eficiência do fotossistema II e maior transporte aparente de elétrons - em relação às plantas do tratamento PA. Houve aumento em K L, maior teor de carboidratos foliares e maior teor de clorofila nas plantas que receberam o dobro da dose recomendada de P, as quais apresentaram maior produção de matéria seca em relação às de PA e P-