Laser-induced ultrasonic guided waves in water-stressed leaves

Abstract

In this work, we studied the properties of acoustic guided waves travelling through plant leaves under water stress. We used a laser-based ultrasound technique to study the relationship between the sample water content and wave propagation characteristics along the midrib and through the lamina. We found that the effective viscoelastic modulus and density in these tissues have different behaviour. Accordingly, we assessed how the acoustic attributes of the guided wave, i.e., the instantaneous phase, attenuation and energy, are modified in both tissues. In addition, we demonstrate that such attributes are highly sensitive to the moisture content and provide quantitative information about the water status of the leaves. As a result, we put forward the use of acoustic vegetal indices as a tool in smart agriculture strategies. This work paves the way to jointly apply commonly used non-destructive techniques to the online and long-distance study of plant hydraulics, as well as the real-time evaluation of the turgor loss point in plants using noncontact methods.