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Abstract

We characterized the responses of plant dry biomass, nitrogen (N) distribution and N-utilization efficiency (NUtE) to changes in CO2 concentration through exposure and culture of winter rape under normal-(380 μmol·mol-1) and elevated-CO2 (760 μmol·mol-1) conditions. Brassica napus (Xiangyou 15) was used as an agriculturally important model plant. Plants were cultivated in a greenhouse with sand culture under normal- (15 mmol·L-1) and limited-N (5 mmol·L-1) conditions. NUtE increased with elevated CO2 regardless of whether N was limited. NUtE was higher under N limitation than under normal N conditions for both normal- and elevated-CO2 conditions. 15N labeling was used to assess the distribution of N from vegetative- to reproductive-organs.Ndistribution within the plant and during different developmental stages was affected by CO2 concentration and the level of N application. A higher proportion of N was found in siliques at the harvest stage for N-limited plants compared to normal-N plants. The proportion of N absorbed into siliques after the stem elongation stage under elevated-CO2 conditions was significantly higher than under normal CO2. The proportion of N transport, as well as the total amount of N, absorbed at the stem elongation stage from vegetative organs into siliques under elevated CO2 was significantly lower than under normal-CO2 conditions. However, the proportion of N absorbed at the stem elongation stage and thus lost from the silique under elevated CO2 was significantly higher than under normal CO2. In conclusion, limited N or elevated CO2 generally benefitted plant NUtE. In addition, after the stem elongation stage, elevated CO2 promoted the redistribution of N from plant vegetative tissues to reproductive organs; however, elevated CO2 during or before stem elongation had the opposite effect.

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