Effects of pre-chilling, incubation temperature and light on seed germination of Saponaria officinalis

Saponaria officinalis L. has been used as a soft cleaning agent and medicinal plant. Understanding germination patterns of seeds of S. officinalis is required for domestication. We examined seed germination behaviors in S. officinalis by pre-treatment with chilling (4 °C), incubation at two constant (20 °C and 25 °C) and an alternating (20 °C/30 °C) temperatures, and incubation in dark and light/dark (8h/16h) conditions. Although the seeds had a seed viability of 96% determined by tetrazolium test, it showed 0.5˜3% of the germination rate at 20 °C and 25 °C in 28 days after incubation. When incubated at 20 °C/30 °C, seeds showed that 75% of the germination rate and 10.2 of the number of days to germination. Pre-chilling promoted seed germination to 85% and 97% in 20 °C- and 20 °C/30 °C-incubation, respectively. The number of days to germination intensively decreased to 7.7 at 20 °C/30 °C. Any positive effect of pre-chilling on seed germination was not found at 25 °C-incubation. Light seemed to have negative effect on seed germination of S. officinalis as the germination rate strikingly decreased to 2.5% in 20 °C- and 75% in 20 °C/30 °C-incubation under light/dark condition despite pre-chilling. These results indicate that pre-chilling and alternating temperature accelerate seed germination of S. officinalis and keeping dark during incubation is more effective.