Enhancing crop yields through improvements in the efficiency of photosynthesis and respiration

The rate with which crop yields per hectare increase each year is plateauing at the same time that human population growth and other factors increase food demand. Increasing yield potential ((Formula presented.)) of crops is vital to address these challenges. In this review, we explore a component of (Formula presented.) that has yet to be optimised – that being improvements in the efficiency with which light energy is converted into biomass ((Formula presented.)) via modifications to CO₂ fixed per unit quantum of light (α), efficiency of respiratory ATP production ((Formula presented.)) and efficiency of ATP use ((Formula presented.)). For α, targets include changes in photoprotective machinery, ribulose bisphosphate carboxylase/oxygenase kinetics and photorespiratory pathways. There is also potential for (Formula presented.) to be increased via targeted changes to the expression of the alternative oxidase and mitochondrial uncoupling pathways. Similarly, there are possibilities to improve (Formula presented.) via changes to the ATP costs of phloem loading, nutrient uptake, futile cycles and/or protein/membrane turnover. Recently developed high-throughput measurements of respiration can serve as a proxy for the cumulative energy cost of these processes. There are thus exciting opportunities to use our growing knowledge of factors influencing the efficiency of photosynthesis and respiration to create a step-change in yield potential of globally important crops.