A NEW EXPLANATION OF THE N CONCENTRATION DECREASE IN TISSUES OF RICE (ORYZA SATIVA L.) EXPOSED TO ELEVATED ATMOSPHERIC PCO_2

摘要

In this paper, four hypotheses to explain the N concentration decrease in plants exposed to elevated pCO_2 were tested by growing rice (Oryza saliva L.) in nutrient solution under two atmospheric CO_2 concentrations (ambient and ambient+200μmol·mol~(-1)) and two N levels (14 and 28mg N·L~(-1)). Results showed that: (1) 'Dilution' of N by enhanced biomass occurred in all tissues but leaves. (2) Elevated pCO_2 favored N allocation to ears over to stems and leaves, however, altered N partition between the shoot and the root was not observed. (3) The decline in transpiration rate should not be the key factor that led to the reduction in plant tissue N concentration under elevated pCO_2. (4) Significantly increased total plant N uptake under elevated pCO_2 did not led to a significant increase of N yield due to increased plant N loss (defined as the difference between total N uptake and N yield). Elevated pCO_2 also decreased root N uptake efficiency (NRE). Increased plant N loss and decreased NRE at elevated pCO_2 may play major roles in N concentration decrease in tissues of rice.