Functional optical coherence tomography in the study of plant-sound interactions

Objective: We aim to test the feasibility of applying Optical Coherence Tomography (OCT), a non-destructive, non-contact, real-time imaging technique to investigate the internal changes within leaves under sound stimulation. Results: Application of a spectral-domain OCT operating at 836.1 nm revealed that depth-resolved images obtained under no sound and under the application of sound stimuli of 100 Hz and 10 kHz sound at 100dB sound pressure to arugula (Eruca sativa) for a minute revealed a clear frequency dependence. The ratio of the OCT structural x-z images of a month-old arugula seedlings was obtained before and after the application of sound. From the ratio images, it was found that the effects under low and high-frequency sounds differed. The low-frequency sound of 100 Hz showed increased activity within the leaf compared to a high frequency of 10 kHz. Our results demonstrate that OCT can potentially investigate the effects of sound in plants speedily and thus has implications in agriculture applications.