Real-time and non-invasive monitoring of plant signaling by means of optical coherence tomography

This work demonstrates the use of optical coherence tomography (OCT) for studying a plant's long-range signaling in real time, <i>in vivo</i>, and non-invasively. This feat is achieved using OCT as a novel technique to visualize minute cellular displacements and deformations within the plant's leaves. The use of bespoke registration algorithms enables tracking displacements with a precision greater than 0.1 μm. This measurement precision is one order of magnitude better than the typical ~1-μm optical resolution of OCT images. In the present work, OCT is used to analyze the time evolution of deformations incurred by wounding. The use of OCT enabled to 1) visualize, in real time, the propagation and evolution of the morphological changes associated with slow wave potentials (onset, peak, and recovery); 2) compute propagation speeds (~0.07 cm s^-1); and 3) distinguish the type of deformation incurred (transient bending of the leaf due to changes in turgor cell pressure). This proof-of-concept study thus exemplifies the potential of OCT as a convenient and complementary tool to study the plant's response mechanisms <i>in vivo</i> and in real time.