Non-invasive optical technique based on speckle phenomenon for application in plant stress physiology

Dynamic properties of biological samples are studied by means of the speckle phenomenon. A non-invasive optical technique for measuring the dynamic response of a tomato leaflet to its detachment from the plant is developed and tested. The technique uses the subtraction of consecutive images of speckle patterns. To quantify changes in the dynamic response of the tested sample, two statistical indicators based on standard deviation are introduced. They allow to analyse the temporal progress of dynamic response in both the whole selected region of the leaflet and different points of this region. Dynamic processes reflecting stress responses passing over the vascular bundle and mesophyll cells of the leaflet are investigated. Although the processes in the vascular bundle gradually cease, the ones in the mesophyll cells exhibit the opposite response to stress. Significant dynamic response heterogeneity is detected within a single leaflet designating this optical technique for opening up a new avenue for non-invasive monitoring of biological samples.