Effects of Low Temperature Treatment of Imbibed Seeds of Eustoma grandiflorum (Raf.) Shinn. on Their Germination and Subsequent Bolting

Research was conducted to determine the effects of various temperatures, their duration, and lighting conditions for imbibed seeds on germination and bolting of Eustoma cultivars. After imbibed seeds of 'Tenryuwhite' were kept for 0, 1, 3 and 5 weeks at 11°C in the dark or light and brought to 30/20°C (day/night), their germination rate increased with low temperature treatments for 3 or 5 weeks compared to the control (with a 50% germination rate). The highest germination rate was 64.9% for the 5-week treatment at 11°C in the dark or light, and then brought to 30/25°C, the respective bolting rate of 'Asukanoasa' and 'Asukanosakura' control plants were 12.5% and 0%. Low temperature treatments for imbibed seeds accelerated bolting of both cultivars. The maximum bolting rate was 100% for 'Asukanoasa' after a 5-week treatment in the dark or 3 weeks in the light, and 85.7% for 'Asukanosakura' for a 5-week treatment in the dark. When imbibed seeds of 'Asukanosakura' were exposed to 2.5, 5, 10, 15°C for 0, 3, 5, 7 weeks, all those kept at 10°C for 5 weeks bolted and flowered, whereas no control plants responded. Hence, the flowering rate of Eustoma seedlings is affected both temperature and its duration.