Fig. 1
From: Non-invasive monitoring of hydraulic surge propagation in a wounded tobacco plant
Principle of the measurement technique. a Divergent light rays diffract at margins of an opaque barrier (plant stem) and form a Fresnel diffraction pattern on a screen behind the stem. b, c Mathematical simulation of the shift of the stem margin and the corresponding diffraction pattern (a.u.—arbitrary units). d A scheme of the optical set-up. Right and left camera recorded the Fresnel diffraction pattern originating at right and left stem margins respectively. The measured tobacco plant was fixed to a pillar post and placed on a movable table driven by a linear actuator, which was connected to a PC. e Measured diffraction patterns from stem and steel rod margins