The photosynthetic light reactions operate as a sensor to pick up changes in the environment and commuicate up-to-the-minute information to the wider cell. This is a vital first step in acclimation and stress tolerance in plants. But what are the specific signalling roles of each photosystem, and what are the impacts of photosynthetic regulation on signalling? In my research, environmental stresses and regulation mutants are combined with transcript and metabolite profiling and photosynthesis analysis to uncover the signalling pathways that respond to changes in photosynthetic energy balance, with a focus on oxylipins and reactive oxygen species.