Influence of rising atmospheric CO2 and phosphorus nutrition on the grain yield and quality of rice (Oryza sativa cv. Jarrah)

Abstract

Raising the atmospheric CO 2 concentration from 350 μl of CO 2 per liter to a level expected by the end of the next century (700 μl/L) influenced both the grain yield and quality of the short-duration rice (Oryza sativa) cultivar, Jarrah. Yield was enhanced by up to 58%, primarily due to an increase in grain number, although grain size was also greater at high CO 2 . Varying the supply of phosphorus influenced the magnitude of the CO 2 response with greatest responses occurring at medium rather than luxury or low phosphorus supplies. However, yield enhancement by high CO 2 was observed even when phosphorus supply was severely growth limiting. Chemical (amylose and nutrient concentration) and physical (relative paste viscosity) measurements made on the ground grain indicated that cooked rice grain from plants grown under high levels of CO 2 would be firmer. The nutritive value of grain was also changed at high CO 2 due to a reduction in grain nitrogen and, therefore, protein concentration. However, total nitrogen content per grain was unaffected by high CO 2 . In contrast, phosphorus content per grain was greater at high CO 2 and there was a strong correlation between magnesium and phosphorus concentrations. These results indicate that there is a need to plan for the inevitable rise in atmospheric CO 2 concentrations by selecting genotypes that will maintain suitable quality characteristics under global change.