Effect of Exposing Imbibed Seeds to Low Temperatures on the Growth and Characteristics of Eustoma grandiflorum

This study was initiated to investigate the effects of exposing imbibed seeds to low temperatures on the growth and characteristics of Eustoma grandiflorum. Two cultivars with different rosette characteristics were used in this experiment, ‘Rococo Marine’ and ‘King of Snow’. Imbibed seeds of both cultivars were stored at a low temperature (10°C) for 5 weeks after sowing or before sowing under dark conditions. After the low-temperature treatment, the seedlings were grown at the natural temperature in the greenhouse for about 1 month. In this period, the daily minimum temperatures ranged from 21.0°C to 25.5°C and the average value was 23.0°C. Moreover, the daily maximum temperature remained in the range of 26.0°C to 43.5°C, within an average temperature of 37.2°C. Irrespective of the rosette characteristics, both cultivars had bolting rates of 100% when the low-temperature treatment was applied. The flower budding and flowering rates were higher than those without the low-temperature treatment in both cultivars. In ‘Rococo Marine’, which has a strong tendency toward rosette formation, the days to bolting, flower budding, and flowering decreased compared with those without the low-temperature treatment. The characteristic forms of the cut flowers were the same irrespective of the low-temperature treatment method. These results demonstrate that it is important to carry out low-temperature treatment of imbibed seeds in the high-temperature season, and that the different low-temperature treatment methods do not affect the growth and characteristics of Eustoma grandiflorum.