The pivotal discovery of a major plant adaptation to a changing climate.

The discovery of the C4 pathway laid the foundations of a revolution in plant biochemistry. The Hatch and Slack paper published in the Biochemical Journal described a specialized pathway of photosynthetic metabolism that minimizes the loss of carbon and nitrogen to maximize efficiency in hot, dry environments. Since that time, there has been an enormous increase in our understanding of the anatomical and biochemical modifications that facilitate C4 photosynthesis in different species. A key feature is the concentration of CO2 in the vicinity of the carboxylating enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, thereby increasing photosynthetic efficiency by minimizing photorespiration. C4 photosynthesis is an excellent model for complex trait evolution in response to environmental change. The C4 pathway represents one of the most convergent of evolutionary phenomena, having evolved independently many times over in diverse families of angiosperms. Climate change is changing the balance between C3 and C4 vegetation types, influencing how ecosystems process carbon and respond to isotope discrimination. Moreover, the pioneering work of Hatch and Slack has formed the biochemical backbone for the C4 rice project, which is one of the most ambitious metabolic engineering initiatives to be attempted in plant science.