[Allocation of rice photosynthates in plant-soil system in response to elevated CO₂ and nitrogen fertilization.]

To examine the allocation of rice photosynthates and its response to the elevated CO₂ (800 μL·L^-1) and N fertilization (100 mg·kg^-1) at both tillering stage and booting stage in plant-soil system, rice was continually labelled with ¹³CO₂. The results showed that the rice root biomass at the tillering stage and the shoot biomass at the booting stage were significantly increased under elevated CO₂. Elevated CO₂ increased the rice biomass and root-shoot ratio at tillering stage, but reduced it at booting stage. Under elevated CO₂, N fertilization promoted shoot biomass during rice growth, but significantly decreased the root biomass at booting stage. Elevated CO₂ significantly increased the allocation of assimilated ¹³C to the soil at the booting stage. N fertilization did not promote the elevated CO₂-induced stimulation of assimilated ¹³C allocated to the soil, and it even decreased the proportion of assimilated ¹³C in the soil. In summary, elevated CO₂ increased the photosynthetic C allocation into soil and promoted the turnover of soil organic carbon in paddy soil. N fertilization enhanced rice shoot biomass but decreased the belowground allocation of photosynthetic C.