Processing of speckle patterns by two methods for the measurement of desiccation in cape gooseberry

The response of Physalis peruviana L (cape gooseberry) seeds to hydration and desiccation was studied by means of the dynamic speckle technique using a low-power laser. A digital camera adapted to a stereoscopic microscope was used to take a series of images of the seeds, being the first time the microscope is used with this technique to study living tissue. The aim was to compare two methods of graphical analysis in processing dynamic speckle images: a) the generalized difference method, slightly modified in the present work, and b) the temporal differences method, being the first time the latter method is applied to seeds. Three groups of seeds were used: live hydrated seeds, live dry seeds, and dry non-viable seeds. The study demonstrates the usefulness of the two methods, confirming previous results showing that the dynamic speckle activity pattern of the hydrated seeds is higher than that of the dry seeds, and that this difference can be measured by digital processing of a series of images. With both methods a pattern of greater activity was detected in the first group of seeds than in the second and third and, additionally, the temporal evolution of the drying process of the hydrated seeds was measured. It is suggested that this technique can be used to develop seed conservation and storage technologies.