Browsing by Person "Ghiasvand Ghiasi, Kambiz"

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    Der Einfluss von Ölgehalt und Fettsäuremuster auf die Lagerfähigkeit von Saatgut
    (2007) Ghiasvand Ghiasi, Kambiz; Kruse, Michael
    Seed storage with the objective of maintaining the quality for the later sowing is a constant challenge, not only in gene banks but also in agriculture, forestry and horticulture. In 1980 ELLIS and ROBERTS established ?The improved seed viability equation? for the prediction of the storability of seeds. With this equation the loss-of-germination-curve can be computed as a function of the initial seed germination, the storage temperature and the seed moisture content for each species. However, with oil-rich seeds the equation very often misses its aim. With this seeds, the variety and lot specific oil content considerably determines water activity and aging rate. Therefore the objective of the present work was to describe the influence of oil content on the aging behavior of seeds of the oil crops during storage quantitatively, to integrate this influence in the most reasonable way into the viability equation and to improve accuracy of its prediction. The investigation was carried out with storage experiments under controlled conditions in the laboratory at higher temperatures and running times between a few days and six months. First it was examined, whether the usually determined oil content of the entire seed is an informative parameter for water activity in the embryo axis. Experiments with sunflowers with an oil content between 28 and 48 % showed that oil-rich seeds need an about 1 % higher seed moisture content than seeds with lower oil content to have the same water activity in the embryonic axis. The storage of these seeds as well as the seeds of rape with oil contents between 39 and 50 % and flax with oil contents between 36 and 43 % showed that the loss of germination is more consistent with uniform water activity than with uniform seed moisture content. This has not been taken into account in the previous viability equation, so that its prediction contains systematic errors. Therefore extensive storage experiments were carried out with altogether 28 seed lots of rape, sunflower, flax and corn with different moisture contents and a uniform temperature of 45°C. Only for few of the stored lots the prediction of the seed viability equation was found to be correct. To include the oil content into the seed viability equation eight different suggestions were compiled. These were applied in three nonlinear regression models with different restrictions to the results of the storage experiments. The first model permitted the species specific determination of the weighing factors (constants) for the seed viability equation. The second model only allowed to determine the weighing factors for the absolute term and the seed moisture content specifically. Oil content was provided however with a species-nonspecific weighing factor. In the third model all weighing factors were species-nonspecific determined. All eight suggestions achieved better estimations for the aging rate in the species-specific models than the previous viability equation. Where this could be examined statistically, the improvements were significant. The same was found for the models with species-nonspecific weighting factors for the oil content. However, not all suggestions led to a converging result of the regression analysis. All examined species-nonspecific models did not improve the adjustment compared to the previous viability equation. The suggestions were then validated with a new and independent dataset with a storage temperature of seeds of 32°C. It was shown that the change of the temperature reduced the accuracy of the estimations of the nonlinear regression models. The new suggestions nevertheless corresponded better to the observed results than the previous viability equation. Based on these results a suggestion was then selected for the extension of the viability equation by ELLIS and ROBERT, which does not introduce a new weighing factor to the equation as the weighing factor might potentially contribute to a decrease of the precision of a prediction due to its standard error. Finally it was examined whether the fatty acid composition before storage in addition to the oil content affects the aging rate and whether the change of the fatty acid composition is directly connected to the loss of germination during storage. Only with rape, significant relations between the proportion of the fatty acid 14:0, 18:0, 20:0, 22:0 and the aging rate of the seed lots were determined. A uniform change of the fatty acid composition of all examined species could not be observed. Therefore this characteristic could not contribute to the further improvement of the prediction accuracy of the seed viability equation. To summarize, a suggestion to include the oil content into the viability equation was designed that clearly improves the accuracy of the prediction of the viability equation for oil-rich seeds and that contributes to a more appropriate and efficient storage of seeds.