Future food requirements: are improvements in photosynthesis required?

Abstract

Carbon dioxide fluxes in agriculture are of global significance because a substantial fraction of the net annual influx provides carbon skeletons for the food that sustains human life and the efflux from crops is associated with their bioenergetics. Those carbon fluxes are linked with atmospheric CO2 concentration, global warming, rates of growth and crop yield. In Asia the population will rise by 1.6 billion over the next fifty years and rice yields will have to rise by 44% simply to keep pace. It is sometimes suggested that CO2 fertilization associated with climate change will lead to increases in yield. However, the yield of the best entry in breeders' trials at the International Rice Research Institute for the past thirty years has not increased and may have actually declined. In this paper several questions are raised. Do crop physiologists really understand enough about the processes shaping yield to clearly identify the yield-limiting problems requiring solutions? How is photosynthesis linked to yield? Can photosynthesis research contribute significantly to attempts to improve rice yield? What advantages, if any, would accrue to agriculture and society if improvements in quantum yield could be made?