Estimation of water stress of plant by vibration measurement of leaf using acoustic radiation force

In order to estimate the water stress of a plant, the natural frequency of the leaf-stalk system was investigated. As a means of vibrating the leaf, acoustic radiation force was utilized, and the successive measurement of the natural frequency of ''komatsuna'', which was cultivated in a pot of soil, was performed for a week until wilting after stopping irrigation. As a result, it was found that the natural frequency is decreased drastically by the wilting of the leaf before the drooping occurs. In addition, daily variation was also observed in the early days, but it was gradually suppressed as the day went on. These behaviors were discussed referring to a simple cantilever beam model. In conclusion, it was ascertained that the acoustic radiation force is efficient for vibrating a leaf-stalk system. Furthermore, it was confirmed that measuring the natural frequency of the leaf-stalk system is effective for the early detection of water stress of a plant.