Influence of leaf physical properties on single-leaf vibrational response to sound

Abstract

Plant leaves respond to environmental sounds by vibration. This study aimed to examine such responses by evaluating the influences of physical properties on vibrational amplitude, velocity and frequency before and during sound stimulation. Nine plant species with a wide range of leaf sizes, qualities and thicknesses and petiole lengths, widths and thicknesses were selected. In the absence of external sound, the leaf amplitude was ~1 μm, the vibrational velocity was ~0.05 mm s-1 and the vibrational frequency was ~0-15 Hz. After sound stimulation, however, the amplitude increased by 1-5.4x, the velocity was 1.75-14.1x higher and produced another spectral peak at ~80-95 Hz. Nevertheless, the amplitude and velocity varied by up to 1-10x among species mainly because of differences in leaf texture. However, these factors did not markedly change in succulent leaves because their thick epidermal cuticles and high water content buffered vibrations. In contrast, leathery leaves and papery and membranous leaves were highly responsive to sound stimuli. Leaf size, mass and thickness and petiole length, width and thickness also influenced leaf vibration. There is a positive correlation between noise reduction and leaf velocity. Noise reduction effect increases with the increase in leaf velocity until about 0.6 mm s-1 and then decreases. The relationship between leaf physical properties and leaf vibration may be used to study sound response and noise reduction in different plant species.