Shining a laser onto biological material produces light speckles, and patterns of such biospeckle activity reflect changes in cell biochemistry, developmental processes and responses to the environment. Ribeiro et al. use a portable laser and a digital microscope to observe in situ biospeckle activity in roots of Zea mays, Jatropha curcas and Citrus limonia, and find that when a root encounters an obstacle the intensity of biospeckle activity decreases abruptly throughout the root system. The response becomes attenuated with repeated thigmostimuli. The data suggest that at least one component of root biospeckle activity results from a biological process, which is located in the zone of cell division and responds to thigmostimuli. The methodology presented is relatively inexpensive and portable, the analysis can be automated and the technique provides a rapid and sensitive functional assay.