One of the most challenging environmental cues that plants face is the water restriction. Thus, understanding what makes plants to avoid such a problem is mandatory. Recently, some results have shown that the hormone peptides rapid alkalinization factor (RALF) might be involved in one of the most important responses to drought: stomatal closure. In this sense, I will investigate these peptide’s functions in Solanum lycopersicum in responde to drought, and what are the mechanisms underlying it. Furthermore, understanding how these peptides interfere with hormones in order to play such roles is also object of my investigation. In order to answer these questions, I will use reverse genetics, biomolecular, biochemical and physiological approaches.