CO 2 elevation and nutrient patchiness interactively affect morphology, nitrogen uptake, partitioning and use efficiency of Nicotiana tabacum L. (tobacco) during anthesis

The stimulation effect of elevated [CO 2 ] ( e [CO 2 ]) on plant growth is modulated by nitrogen (N) availability, yet the mechanisms of this modulation under patchy N supply remain largely elusive. This study aimed to investigate the mechanisms by which patchy nutrient supply in the root‐zone influence on N uptake, partitioning and use efficiency of tobacco plants ( Nicotiana tabacum L.) grown under e [CO 2 ]. A split‐root pot experiment was conducted on tobacco plants grown at ambient ( a [CO 2 ], 400 μmol L −1 ) and e [CO 2 ] (800 μmol L −1 ) conditions during anthesis. Plants were subjected to two fertilizer levels [0 and 113‐29‐214 (N‐P‐K) mg kg −1 soil] and three fertilization regimes (partial root‐zone fertilization, PRN, couple root‐zone fertilization, CRN and no fertilization, CK). Elevated [CO 2 ] significantly decreased N concentrations in all tobacco organs, with the greatest reduction in leaves. Positive responses of tobacco biomass and NUE to e [CO 2 ] were recorded, and a large amount of 15 N labelled fertilizer‐N was partitioned to stems at the expense to leaves. Compared to the partially fertilized root, an equal N concentration was observed in the non‐fertilized root. In addition, compared with CRN, PRN increased the root exudates of sugar and organic acid; however, the increased root biomass by nutrient patchiness did not enhance plant total N uptake. Collectively, e [CO 2 ] could sustain N assimilation and distribution of tobacco plants in response to natural heterogeneous nutrient available in the soil caused by patchy fertilization.