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  • Author or Editor: Angéla Anda x
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The aim of the study was to analyse the effect of atmospheric cadmium (Cd) pollution of atmospheric origin in maize compared to a control without Cd pollution. The plant parameters investigated were the timing of phenological phases, leaf area index (LAI) and yield, while radiation and water regime parameters were represented by albedo (reflection grade) and evapotranspiration, respectively. In treatments with and without irrigation, Cd caused a significant reduction in LAI, accompanied by lower evapotranspiration. The mean annual albedo in the Cd-polluted treatment only rose to a moderate extent in 2011 (in 2010 there was hardly any change), but changes within the year were more pronounced in certain phases of development. Cd led to greater reflection of radiation by plants during the vegetative phase, so the radiation absorption of the canopy was reduced leading to a lower level of evapotranspiration. In the dry, hot year of 2011 maize plants in the non-irrigated treatments showed a substantial reduction in grain dry matter, but maize yield losses could be reduced by irrigation in areas exposed to Cd pollution.

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In the present explorative study, different time-series analysis methods, such as moving average, deterministic methods (linear trend with seasonality), and non-parametric Mann–Kendall trend test, were applied to monthly precipitation data from January 1871 to December 2014, with the aim of comparing the results of these methods and detecting the signs of climate change. The data set was provided by the University of Pannonia, and it contains monthly precipitation data of 144 years of measurements (1,728 data points) from the Keszthely Meteorological Station. This data set is special because few stations in Hungary can provide such long and continuous measurements with detailed historical background. The results of the research can provide insight into the signs of climate change in the past for the region of West Balaton. Parametric methods (linear trend and t-test for slope) for analyzing time series are the simplest ones to obtain insight into the changes in a variable over time. These methods have a requirement for normal distribution of the residuals that can be a limitation for their application. Non-parametric methods are distribution-free and investigators can get a more sophisticated view of the variable tendencies in time series.

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Hydroxamic acids (HAs) are plant secondary metabolites produced by certain cereals, which have been found to be toxic to pest aphids in artificial diet assays. Previous studies have shown that tetraploid and hexaploid wheat varieties, the leaf tissues of which contained higher levels of these compounds than used in artificial diets, did not reduce aphid settling or fecundity. This current study reports findings on a high HA producing B genome accession of the diploid ancestor of wheat, Aegilops speltoides. We found that this accession does have a negative impact on aphid host selection and substantially reduces nymph production. Whole leaf tissue assays showed very high levels of HAs, well in excess of the toxic level determined in the artificial diet assays. Extraction of the apoplast fluid (AF) from this accession showed that the HA level is much lower than that of the whole tissue, but is still close to the artificial diet toxic level. Furthermore the HA level in the AF increases in response to aphid feeding. These observations could explain why hexaploid wheat remains susceptible to aphids, despite having whole leaf tissue HA levels in excess of the toxic levels determined in artificial diets.

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