Concurrent exposure to water deficit and elevated ambient temperature alleviates root growth defects in Arabidopsis

Plants are often simultaneously subjected to different environmental stresses threatening their very existence. As high temperature events usually coincide with drought conditions, a combination of these stresses is a common occurrence in the field. Recently, global warming has led to an increase in the frequency and intensity of heatwaves and drought across the globe, severely compromising plant performance. However, our understanding of root system responses to combined stress scenarios is limited. Hence, in this study, we investigated how the root system responds under a combined stress environment comprising of elevated ambient temperature and water deficit. We found that a positive effect, likely from, interaction between these two important environmental stresses mitigates root growth defects. Interestingly, this interaction effect appears to be specific to the root system. Furthermore, our results demonstrate that auxin signaling pathway is critical for this response. Data reveal that combined stress alleviates the disruption in auxin level and its crosstalk with ethylene induced by elevated ambient temperature in the root meristem. ELONGATED HYPOCOTYL5 (HY5), is also involved in this process by modulating redox homeostasis. Collectively, our findings suggest a framework for understanding how root systems respond to a combined stress environment associated with global warming and climate change.