The turgor loss point (TLP), which is considered a threshold for many physiological processes, may be useful in plant-breeding programs or for the selection of reforestation species. Obtaining TLP through the standard pressure–volume (p–v) curve method in a large set of species is highly time-consuming and somewhat subjective. To solve this problem, we present an objective and a less time-consuming technique based on the leaf resonance able to calculate the relative water content (RWC) at TLP (RWCTLP). This method uses air-coupled broadband ultrasonic spectroscopy to obtain the sigmoidal relation between RWC and the standardized resonant frequency (f/fo). For the 13 species measured, the inflexion point of the RWC–f/fo relationship (
) was not statistically different from the value of RWC at the TLP obtained with the p–v curves (RWCTLP p–v).