Stress response, cell death and signalling: the many faces of reactive oxygen species

Plants respond to pathogens and abiotic stresses by transient increases in the production of reactive oxygen species (ROS) and ion fluxes, which activate both local programmed cell death and systemic increases in stress‐ and pathogen‐resistance. The present essay explores the emerging complexity of the multiple roles that ROS play in intra‐ and intercellular communication in both stressed and unstressed organisms.