Atmospheric CO₂ enrichment is expected to affect the resource use efficiency of C3 plants with respect to water, nutrients and light in an interactive manner. The responses of oilseed rape (OSR) to elevated CO₂ have not much been addressed. Since the crop has low nitrogen use efficiency, the interactive effects of CO₂ enrichment and nitrogen supply deserve particular attention. Spring OSR was grown in climate chambers simulating the seasonal increments of day length and temperature in South-Western Germany. Three levels of N fertilisation representing 75,150 and 225 kg ha^-1 and two CO₂ concentrations (380 and 550 μmol mol^-1) were used to investigate changes in source-sink relationships, plant development and senescence, water use efficiency of the dry matter production (WUE_prod.), allocation patterns to different fractions, growth, yield and seed oil contents. Seven harvests were performed between 72 and 142 days after sowing (DAS). Overall, plant performance in the chambers was comparable to the development under field conditions. While CO₂ responses were small in the plants receiving lowest N-levels, several significant N × CO₂ interactions were observed in the other treatments. Increasing the N availability resulted in longer flowering windows, which were furthermore extended at elevated CO₂ concentrations. Nevertheless, significantly less biomass was allocated to reproductive structures under elevated CO₂, while the vegetative C-storing organs continued to grow. At the final harvest shoot mass of the CO₂ exposed plants had increased by 9, 8 and 15% in the low, medium and high N treatments. Root growth was increased even more by 17, 43 and 33%, respectively and WUE_prod. increased by 23, 42 and 35%. At the same time, seed oil contents were significantly reduced by CO₂ enrichment in the treatments with ample N supply. Obviously, under high N-supply, the CO₂ fertilisation induced exaggerated growth of vegetative tissues at the expense of reproductive structures. The interruption of source-sink relationships stimulated the formation of side shoots and flowers (branching out). While direct effects of elevated CO₂ on flowering can be excluded, we assume that the increased growth under high N and CO₂ supply created nutrient imbalances which hence affected flowering and seed set. Nevertheless, the final seed macronutrient concentrations were slightly increased by elevated CO₂, indicating that remobilisation of nutrients from the sources (leaves) to the sinks (seeds) remained effective. These findings were supported by the lower nitrogen concentrations in senescing leaves and probably increased N remobilisation to other plant parts under elevated concentrations of CO₂. All the same, CO₂ enrichment caused a decline in seed oil contents, which may translate into a reduced crop quality.

EXPLOR_STEP=$WICRI_ROOT/Wicri/Musique/explor/MozartV1/Data/PascalFrancis/Corpus

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{{Explor lien
   |wiki=    Wicri/Musique
   |area=    MozartV1
   |flux=    PascalFrancis
   |étape=   Corpus
   |type=    RBID
   |clé=     Pascal:11-0321670
   |texte=   Growth, senescence and water use efficiency of spring oilseed rape (Brassica napus L. cv. Mozart) grown in a factorial combination of nitrogen supply and elevated CO2
}}