The art of multi-tasking: plant responses to their environment

Plant growth, development and survival are a continuous balancing act, integrating numerous environmental signals with core developmental programs. Nevertheless, in plant physiological research we usually study responses to the environment one factor at the time. It was the advent of microarray-based transcriptomics, and specifically the demonstration that combined treatments produce unique transcriptional signatures, that transformed stress combination into a defined molecular research program. We highlight how the field has evolved from the first seminal reports that combined severe abiotic stress treatments to a more comprehensive understanding of plant response to a range of conditions, including temperature, water availability, nutrients and light. We propose to broaden the conceptual framework from "combined stress" to a more inclusive consideration of context-dependent integration of environmental signals into responses. Integration of dose-, time- and location-dependent responses to the key plant hormones auxin, abscisic acid, ethylene and jasmonate are discussed. To further this research domain, we recommend accurate recording of environmental conditions and routine incorporation of treatment gradations, from mild to severe, in our research. Realizing this integrative view will require combining data-rich omics and machine-learning approaches with focused, hypothesis-driven experiments.