New article about the application of air-coupled ultrasound to monitor variations in leaf properties caused by plant responses to different environmental stimuli (light intensity variations, watering after a drought period, diurnal cycles…):
Fariñas, M. D., Knapik, D. S., Pina, J. J. P., Pelegrin, E. G., & Álvarez-Arenas, T. E. G. (2014). Monitoring Plant Response to Environmental Stimuli by Ultrasonic Sensing of the Leaves. Ultrasound in medicine & biology, 40(9), 2183-2194.
Evolution of the thickness resonant frequency of a Vitis vinifera leaf over 3.5 days. Photosynthetic photon flux (PPF) and ambient temperature measurements are also shown.