Elevated atmospheric CO(2) concentration triggers redistribution of nitrogen to promote tillering in rice

Elevated atmospheric CO(2) concentration (eCO(2)) often reduces nitrogen (N) content in rice plants and stimulates tillering. However, there is a general consensus that reduced N would constrain rice tillering. To resolve this contradiction, we investigated N distribution and transcriptomic changes in different rice plant organs after subjecting them to eCO(2) and different N application rates. Our results showed that eCO(2) significantly promoted rice tillers (by 0.6, 1.1, 1.7, and 2.1 tillers/plant at 0, 75, 150, and 225 kg N ha(−1) N application rates, respectively) and more tillers were produced under higher N application rates, confirming that N availability constrained tillering in the early stages of growth. Although N content declined in the leaves (−11.0 to −20.7 mg g(−1)) and sheaths (−9.8 to −28.8 mg g(−1)) of rice plants exposed to eCO(2), the N content of newly emerged tillers on plants exposed to eCO(2) equaled or exceeded the N content of tillers produced under ambient CO(2) conditions. Apparently, the redistribution of N within the plant per se was a critical adaptation strategy to the eCO(2) condition. Transcriptomic analysis revealed that eCO(2) induced less extensive alteration of gene expression than did N application. Most importantly, the expression levels of multiple N‐related transporters and receptors such as nitrate transporter NRT2.3a/b and NRT1.1a/b were differentially regulated in leaf and shoot apical meristem, suggesting that multiple genes were involved in sensing the N signal and transporting N metabolites to adapt to eCO(2). The redistribution of N in different organs could be a universal adaptation strategy of terrestrial plants to eCO(2).