[Allocation of rice photosynthates in plant-soil system in response to elevated CO 2 and nitrogen fertilization.]

To examine the allocation of rice photosynthates and its response to the elevated CO ₂ (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 ¹³ CO ₂ . 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 CO ₂ . Elevated CO ₂ increased the rice biomass and root-shoot ratio at tillering stage, but reduced it at booting stage. Under elevated CO ₂ , N fertilization promoted shoot biomass during rice growth, but significantly decreased the root biomass at booting stage. Elevated CO ₂ significantly increased the allocation of assimilated ¹³ C to the soil at the booting stage. N fertilization did not promote the elevated CO ₂ -induced stimulation of assimilated ¹³ C allocated to the soil, and it even decreased the proportion of assimilated ¹³ C in the soil. In summary, elevated CO ₂ 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.