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| Dissertation / PhD Thesis/Book | PreJuSER-46949 |
2006
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 3-89336-464-1
Please use a persistent id in citations: http://hdl.handle.net/2128/2575 http://hdl.handle.net/2128/2484
Abstract: In this work the impact of heterogeneously distributed nutrients on plants was examined. In splitroot experiments Zea mays plants (Zea mays hybrid Helix) received the same amounts of nutrients, with different fractions supplied to each root compartment (0.5/0.5, 0.6/0.4, 0.7/0.3, 0.8/0.2, 0.9/0.1, 1.0/0.0). The amounts of nutrients were adapted to the relative growth rate (RGR) of this species in order to achieve a nutritional supply adapted to demand. Two different experiments were run. In one experiment the amount of nutrients was adapted to 1.5*RGR, in another experiment to 0.5*RGR. With this experimental design, it was possible to measure at what level of nutrient heterogeneity plants responded and if these responses were influenced by the total amounts of given nutrients. In addition, the impact of nutrient heterogeneity on structural and functional parameters was measured. The experiments indicated that plants responded locally to nutrient heterogeneity by changes in biomass, and that this response depended on the nutrient status of the plants. Well fertilized plants responded with different root biomass at a ratio of nutrient supply of 0.6/0.4. In contrast to this, plants with a lack of nutrients responded to an unequal supply of nutrients in the 0.7/0.3 treatment. The ratio of given nutrients in the root compartments were probably not responsible for this different reaction, however, because the response was possibly caused by a minimum difference of supplied nitrate concentrations in the split root sides within the treatments. If this difference in concentration was exceeded long enough (> 4 days), plants responded. Nutrient heterogeneity had no impact on the total plant, total root and shoot biomass. But the nutrition status of the plants influenced the shoot biomass. Well fertilized plants had higher shoot biomass than plants under nutrient deprivation. This was detectable in different shoot/root ratios, too. In this work different functional parameters of plants with heterogeneous nutrient supply were measured. Neither the rate of photosynthesis nor the sugar and starch concentrations in leaves and roots were influenced. On the other hand with increasing heterogeneity, the concentration of nitrogen in the above ground part of the plants as well as in the total plant increased. In contrast to this, the sulphur concentrations in the plants were not influenced. This could be explained with different uptake systems for nitrogen and sulphate and their distribution in the roots. Furthermore the amino acid concentration in the leaves was influenced by the heterogeneous distribution of supplied nutrients. Irrespective of the nutritional status of the plants, the control treatments (0.5/0.5) showed lower total amino acid concentrations compared to the 1.0/0.0 treatment. In this work it was demonstrated that the amount of supplied nutrients had a stronger impact on plant behaviour than their distribution. If plants responded structurally as well as functionally to nutrient heterogeneity, these responses were partly influenced by the nutritional status of the plants, occurred locally and at the whole plant level.
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