Effects of soaking period and gibberellic acid addition on caper seed germination

In order to improve caper seed germination, this two-year study (2005-2006) was designed to determine the effects of seed soaking treatments and soaking times, individually or in combination with the addition of gibberellic acid to the germination substrate. Besides testing the control seeds, 7 soaking periods were assayed, soaking seeds in tap water at room temperature for 24 h, 15, 30, 45, 60, 75 and 90 days. Germination tests were performed in closed Petri dishes in a growth chamber. Germination data were fitted to the logistic function and calculations were made for the maximum germination percentage, the time to reach 50% of final germination and the mean relative cumulative rate. A soaking period of 30 days or longer enhanced seed germination; final germination values ranged from 95 to 99%, reducing the time to reach 50% of final germination and consequently the duration of germination tests. Addition of gibberellic acid to the substrate after soaking improved germination only for control seeds and those soaked for 24 h or 15 days. Seed soaking for 30 or 45 days, followed or not by the addition of a gibberellic acid solution to the substrate, is an efficient method to enhance caper seed germination.