Effect of ultrasonic waves on seed germination of Capparis spinosa L. as related to exposure time, temperature, and gibberellic acid

The effects of ultrasonic waves (1700 KHz) on germination of Capparis spinosa L. seeds are reported. Only the seeds previously scarified with sulphuric acid responded to the ultrasonic treatments. A specially prepared apparatus made it possible to carry out the ultrasonic treatments in water at controlled temperatures. A significant increase in germination percentage was found for exposure times from 10 min to 6 hr. Optimal temperatures for the treatment were 25 and 30°C. The highest germination percentages (above 50%) were obtained when ultrasonic treatment was carried out in the presence of gibberellic acid (400 mg.l-1). Significant differences for average germination time did not emerge from the trials. Various hypotheses are advanced to explain the mechanism of action of ultrasonic waves. The acquired information, however, supports the concomitant and/or sequential effect of more than one action, at both a physical and biochemical level. The importance of provenance of the seed population is also underlined.