Professor John Evans is internationally renowned for elucidating the nitrogen economy of photosynthesis. He has shown how photosynthetic adaptations of species to environmental conditions become quantitatively manifest in the allocation of nitrogen to biochemical processes. He has applied these relationships to photosynthetic processes across scales as diverse as chloroplasts, individual leaves and plant canopies. His seminal work on CO2 diffusion within leaves forms a basis for process-based models of plant productivity in relation to global change, and the intellectual framework for molecular research aimed at raising crop yields by engineering photosynthesis.