Laser biospeckles as a speedy tool to investigate the effects of sound on lentil (Lens esculenta puyensis) seeds.

OBJECTIVE: We propose the application of laser biospeckles-a non-destructive, non-contact, real-time technique-to investigate the effect of sound pressure levels and different frequency sounds on lentil (Lens esculenta puyensis) seeds. Lentil seeds were illuminated by a laser diode source with a wavelength of 630 nm, and biospeckle patterns resulting from the interference of scattered laser light were captured as time-sequenced image frames. Biospeckles were recorded under white noise as well as under different frequencies of 100 Hz, 1 kHz, and 10 kHz at 80 dB. The time-sequenced frames were analyzed for the effects of sound by calculating the correlation between the frames and were characterized by a parameter called BA (Biospeckle Activity), which reflects the level of internal activity within the seeds. RESULTS: We found that the BA value was lower under white noise, indicating reduced activity within the seeds. Furthermore, a clear dependence of BA on sound frequency was observed, with this trend becoming apparent after six hours-well before visible germination began. It was found that, depending on the frequency applied, lentil seed germination could either be accelerated (e.g., at 1 kHz) or decelerated (e.g., at 100 Hz or 10 kHz). These results suggest that the laser speckle method may enable faster characterization of the characteristic frequency response of different plant seed species.