Ultrasound Pulse Emission Spectroscopy Method to Characterize Xylem Conduits in Plant Stems

Although it is well known that plants emit acoustic pulses under drought stress, the exact origin of the waveform of these ultrasound pulses has remained elusive. Here, we present evidence for a correlation between the characteristics of the waveform of these pulses and the dimensions of xylem conduits in plants. Using a model that relates the resonant vibrations of a vessel to its dimension and viscoelasticity, we extract the xylem radii from the waveforms of ultrasound pulses and show that these are correlated and in good agreement with optical microscopy. We demonstrate the versatility of the method by applying it to shoots of ten different vascular plant species. In particular, for Hydrangea quercifolia, we further extract vessel element lengths with our model and compare them with scanning electron cryomicroscopy. The ultrasonic, noninvasive characterization of internal conduit dimensions enables a breakthrough in speed and accuracy in plant phenotyping and stress detection.

Automated summary

This study investigates the waveform characteristics of ultrasound pulses emitted by plants under drought stress and correlates them with the dimensions of xylem conduits. By using a model that relates the vibrations of a vessel to its dimension and viscoelasticity, the researchers extract the xylem radii from the ultrasound pulse waveforms and show their correlation with optical microscopy. The versatility of the method is demonstrated by applying it to shoots of ten different vascular plant species, and vessel element lengths are further extracted and compared with scanning electron cryomicroscopy for Hydrangea quercifolia. The noninvasive characterization of internal conduit dimensions using ultrasound enables faster and more accurate plant phenotyping and stress detection.