High temperatures modify plant responses to abiotic stress conditions.

Climate change is altering environments in which plants and different crops grow and survive. We already experienced an increase in worldwide average earth surface temperatures, as well as frequency and extent of damaging heat waves. These conditions collide in the field with other abiotic stresses such as water deficit, high salinity, increased light irradiation, and so on, generating complex harmful conditions that destabilize agricultural systems. The conditions generated during these episodes of stress combination greatly differ from those occurring in the field when different stress factors occur individually; conditions that have been the focus of study for decades. Fortunately, knowledge of physiological and molecular responses to stress combinations and the cost they inflict on plant growth and yield has been exponentially increasing in the past several years. Understanding plant performance under multiple stress combinations will allow breeding crops capable of maintaining yield production under the new climatic conditions. Here, after reviewing recent data on physiological, hormonal and transcriptional responses to different stress combinations, we highlight the importance of photodamage avoidance, abscisic and jasmonic acid signaling, and the upregulation of genes involved in oxidation-reduction processes, photosynthesis and protein metabolism, for plant acclimation to conditions of high temperatures, in combination with other common abiotic stress factors such as drought or salinity. Finally, we propose new approaches to investigate the response of plants to stress combinations and discuss strategies for improving crop resilience to stress combination.