FACE-ing the global change: Opportunities for improvement in photosynthetic radiation use efficiency and crop yield

The earth is rapidly changing through processes such as rising [CO2], [O3], and increased food demand. By 2050 the projected atmospheric [CO2] and ground level [O3] will be 50% and 20% higher than today. To meet future agricultural demand, amplified by an increasing population and economic progress in developing countries, crop yields will have to increase by at least 50% by the middle of the century. FACE (Free Air Concentration Enrichment) experiments have been conducted formore than 20 years in various parts of world to estimate, under themost realistic agricultural conditions possible, the impact of the CO2 levels projected for the middle of this century on crops. The stimulations of crop seed yields by the projected CO2 levels across FACE studies are about 18% on average and up to 30% for the hybrid rice varieties and vary among crops, cultivars, nitrogen levels and soil moisture. The observed increase in crop yields under the projected CO2 levels fall short of what would be required to meet the projected future food demand, even with the most responsive varieties. Crop biomass production and seed yield is the product of photosynthetic solar energy conversion. Improvement in photosynthetic radiation use efficiency stands as themost promising opportunity allowing formajor increases in crop yield in a future that portendsmajor changes in climate and crop growing environments. Our advanced understanding of the photosynthetic process along with rapidly advancing capabilities in functional genomics, genetic transformation and synthetic biology promises new opportunities for crop improvement by greater photosynthesis and crop yield. Traits and genes that show promise for improving photosynthesis are briefly reviewed, including enhancing leaf photosynthesis capacity and reducing photorespiration loss, manipulating plant hormones’ responses for better ideotypes, extending duration of photosynthesis, and increasing carbon partitioning to the sink to alleviate feedback inhibition of photosynthesis. 2009 Elsevier Ireland Ltd. All rights reserved.