This book will highlight the tremendous potential of treating plants with signaling molecules, either prior to or during stress, in lowering oxidative damages and causing enhanced tolerance during stress conditions. The latest research on the ability of different signalling molecules enhancing the growth and in reducing the effects of abiotic stresses in different crop species, together with their mechanism of action at the biochemical and molecular level will be emphasized. Such documentation of signalling and crosstalk of the different signalling molecules will stimulate further research towards fully exposing their way of action, which, in turn, would be of great significance for plant stress physiology research. In addition, focusing on specific challenges and opportunities related to this exogenous application or priming technology, such as the mode of application, new methodologies and the potential impacts of signalling molecules on the environment, will result in the optimum and rapid establishment of this technology as a tool in crop stress management. The book will foster further interests for researchers, academics and scientists worldwide, working in the field of novel application of signaling and crosstalk of signaling molecules.