Growth, grain yield and quality of rice (Oryza sativa L.) in response to elevated CO_2 and phosphorus nutrition

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The influence of rising atmospheric CO_2 concentrations and phosphorus nutrition on growth, grain yield and quality of a early maturing rice cultivar (Oryza sativa L. cv. Jarrah) was investigated by growing plants in a range of phosphorus levels at either 350 or 700μL CO_2 L^<-1> in the growth chambers. Total above ground biomass and grain yield were greater at elevated CO_2 concentrations and with increasing phosphorus supply. The CO_2 response was evident at all but the lowest phosphorus treatments but its magnitude was greater at moderate phosphorus supplies. The increase in grain yield at high CO_2 was due mainly to an enhancement of tiller number. The phosphorus concentration in the foliage was unaffected by CO_2 enrichment and the critical concentration of 1.8 g kg^<-1> dwt was the same as reported for field-grown rice. The concentration of calcium in the foliage was increased by high CO_2 and the nitrogen concentration was reduced. Chemical analysis (amylose and mineral concentration) indicated that cooked rice grain from high-CO_2-grown plants would be firmer and that concentrations of Zn and Fe, which are important in the diet of humans, will be lower. These results indicate that there is a need to plan for the inevitable rise in global CO_2 concentrations by selecting cultivars which will be more productive and yet maintain suitable quality characteristics under elevated CO_2 levels.
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