Effects of Light Intensity and Temperature on Devernalization of Japanese Radish

Abstract

The effects of light intensity and temperature on devernalization of Japanese radish were studied. Seeds of the ′Minowase′ radish were sown under dark condition of 25°C growth chamber for two days. The germinated seeds were then subjected to a 3×3 factorial treatment combination, consisting of three levels of day/night temperature (5/5, 20/5, and 30/5°C) and three levels of light intensity (5, 10, and 30klux) for 21 days. The day length was 12 hours. After the treatments, the plants were transplanted into water culture beds in a glasshouse for observing the flowering behavior.
The result showed that under the completely vernalizing condition (5/5°C), various levels of light intensity tested had no effect on rate of bolting and flowering or the number of leaves at anthesis. In the plants treated under the partially vernalizing condition (20/5°C), in contrast, the high light intensity (30klux) showed an additive devernalizing effect in delaying the rate of bolting and flowering. There was a significant difference in the number of leaves at anthesis among the plants exposed to different light intensities under the 20/5°C temperature condition. Less than 20% of the apex of plants treated with the various light intensities under the devernalizing condition (30/5°C) were observed in the dome-shaped stage at the termination of the experiment. The present findings suggest that the degree of devernalization can be reduced either by lowering day temperature or light intensity, or both.