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  • Author or Editor: B. Hoffmann x
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In Hungary 53% of wheat ( Triticum aestivum L.) cultivars registered during the last twenty years carry the 1RS translocation, the short arm of rye ( Secale cereale L.) chromosome 1. Wheat production in Hungary is limited primarily by drought. Despite the widespread use of this translocation there is no information about its effect on stress tolerance. The objective of this study was to investigate the effect of 1BL. 1RS on drought tolerance. ‘Mv5791-1B.1R’ and the sister line ‘Mv5791-1B.1B’ were examined among other cultivars in greenhouse under well-watered and drought conditions. Data were obtained for anthesis-and maturity date, plant height, root/shoot ratio, components of grain yield, Harvest Index (HI) and Water Use Efficiency (WUE). The translocation line had higher root-and shoot dry weight in both treatments and an increased root/shoot ratio, which was more than the sister line in dry treatment (69 and 38%, respectively). The larger root biomass of the 1RS translocation line could contribute to the increased HI and WUE under drought that resulted in less yield decrease (23 and 32%, respectively) compared with the non-translocation counterpart.

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Abstract  

On the basis of calculations using a simple model of the energetic heterogeneity of a solid surface (assuming linear dependence of activation energy of desorption of the reactant on the degree of coverage), it is shown that both the degree of conversion and the course of desorption of the reactants are strongly influenced by the degree of heterogeneity assuming non-isothermal conditions. In contrast to a homogeneous solid surface, the degree of conversion for a heterogeneous surface depends strongly on the initial coverage of a catalyst by reactant. Possibilities for kinetic evaluation are indicated from the modelling calculations.

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By means of model calculations it could be shown for an irreversible surface reaction of 1st order that the determination of the activation energy of the desorption of the reactant or, respectively, of the surface reaction is possible by application of the method of variation of the heating rate to the desorption curve of the reactant, according to circumstances whether the ratio of the activation energy of the surface reaction and of the desorption of the reactant is greater or smaller than one.

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Through simulation of TPD model curves for desorption from adsorption sites of different strength could be shown that the use of non-linear temperature programmes influences the complex desorption process in such a manner that the appearing desorption maxima are better visible.

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TPD studies on the kinetics of deammoniation of an NH4NaY zeolite showed that the use of a hyperbolic temperature programme led to kinetic parameters agreeing with those resulting from a linear heating process. Because of the progressive increase of the heating rate in the case of hyperbolic heating schedules, the parameters can be considered as independent of the heating rate within certain limits. The better resolution of complex desorption spectra with hyperbolic programmes is an additional reason for their use.

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The new stem rust strain, Puccinia graminis f. sp. tritici — Ug99, has been a rising threat since the alarm was rung in Uganda in 1998. The genetic and breeding dimensions of research against this disease include the development of vigorous molecular markers, the identification and introgression of multiple resistance genes, the translocation of alien chromosomes, the enrichment of breeding lines with crossability alleles and the development of interspecific hybrids. Resistance genes have been identified in the primary wheat gene pool and in alien sources such as Aegilops spp., Dasypyrum villosum, Secale cereale, Hordeum vulgare and Oryza spp. and some of these sources have been used to confer resistance as a function of single or multiple gene effects. Realizing the potential disaster if Ug99 and related variants break out in other regions, wheat-producing countries are characterizing their germplasm and improving their stem rust race tracking systems. Equally important is “appropriate genetic management”, i.e. the use of currently effective resistance genes in such a way that the evolution and adaptation of new virulence will be deterred. This review will summarize the recent research advances and future perspectives in setting effective genetic barriers vis-à-vis the seemingly intractable spread and evolution of Ug99.

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Curves of the temperature-programmed desorption (TPD) of ammonia from zeolites were evaluated with several kinetic models. An approximately linear correlation was found between the activation energy of desorption or the heat of adsorption of H zeolites with various Si/Al ratios and the intermediate electronegativity of the zeolites, the latter representing a measure of the acid strength.

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The splitting of water in the temperature range from 470 to 970 K was studied for a series of CoNaX zeolites of a Si/Al ratio of 1.18 and of different degree of exchange and at the parent type NaX. In case of CoNaX zeolites peaks at about 570 and 670 K and a broad flat peak at even higher temperatures could be observed. Both the first peaks are ascribed to the process of dehydroxylation between CoOH and structural OH groups, the latter to the dehydroxylation between structural OH groups only. The parent type provided only a single peak with a maximum at about 570 K.

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The temperature-programmed desorption (tpd) of the amount of ammonia which is preadsorbed at about 373 K at HZSM-5 zeolites yields a complex desorption curve consisting of two overlapped peaks (Β andγ peak). Parts of the ammonia desorbed can be attributed to SiOHAl groups considering also1H-MAS NMR measurements.

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