Shorter and more efficient pretreatment for germination of perilla mericarps.

Perilla (Perilla frutescens (L.) Britton) mericarps are known to undergo dormancy; however, this can be broken by sulfuric acid treatment and cold stratification. Cold stratification is thought to be the most effective treatment and is customarily performed for 2 weeks to induce germination of perilla mericarps. However, this procedure requires an additional 2 weeks before sowing and cultivation, thereby decreasing cultivation efficiency. To address this problem, germination experiments were conducted in this study in order to identify a shorter and more efficient pretreatment strategy for germination of perilla mericarps. Pretreatment with sulfuric acid (10 min versus 1 min) and gibberellin (8 h and 1 h versus 5 min, at a rate of 100 versus 10 ppm) were performed using mericarps from pure strains of perilla. As a result, sulfuric acid treatment tended to reduce the germination rate, while gibberellin treatment resulted in an equivalent or similar germination rate as cold stratification. Gibberellin treatment was also found to be effective in mericarps with a relatively old harvest date and low germination energy. Considering the convenience and safety of the treatment process as well as the results of the germination experiments, these findings suggest that a short period of gibberellin treatment could help shorten the process of perilla cultivation.