Environmental stresses significantly hinder plant growth and productivity, with global climate change exacerbating the issue. In response to stress, plants activate a signaling cascade, involving multiple molecules ultimately leading to resistance or stress adaptation. However, the temporal ordering and composition of the resulting cascade, and the specific stress it encodes for, remain largely unknown. In this study we multiplexed nanosensors for H2O2 (key signalling molecule) and Salicylic acid (SA) (stress hormone) for simultaneous monitoring of stress-induced H2O2 and SA signals when Brassica rapa subsp. Chinensis (Pak choi) plants were subjected to distinct stress treatments, namely light stress, heat stress, pathogen stress and mechanical wounding in real time. Nanosensors reported distinct dynamics and temporal wave characteristics of H2O2 and SA generation for each stress providing novel scientific insights on the interplay among stress signalling molecules mediating stress responses. Further, plants emit volatile organic compounds (VOCs) which serve as the major mediators of information transfer between plants. Such VOC-mediated interplant communication can affect the growth and defence response of the receiver plant. However, the mechanisms of VOC sensory transduction to elicit downstream metabolic responses remains elusive. We used SA and H2O2 nanosensors to visualize their generation in Brassica rapa subsp. Chinensis (Pak choi) plants, following exposure to constitutively-released VOCs from neighbouring aromatic plants – namely sweet basil and spearmint. Within 2 h of exposure to VOCs from both aromatic plants, ROS and SA production were observed in Pak choi, but each VOC blend triggered unique temporal signatures of ROS and SA generation which lead to different physiological responses in receiver Pak Choi. Overall, our study demonstrates that sensor multiplexing can be a transformative strategy to investigate stress signaling mechanisms in plants, aiding in developing climate-resilient crops and pre-symptomatic stress diagnoses and for a deeper understanding of plant-plant communication to advance sustainable agriculture.
