Abstract
Effect of DIF (Difference between day and night temperature) on hypocotyl elongation of Brassica oleracea var. acephala. was analyzed by image processing. Experiments were conducted under three DIF conditions,namely 15/25°C, 20/20°C and 25/15°C in growth chambers where photosynthetic photon flux (PPF) of 150μmol s-1 m-2 on the canopy level with a 12 h photoperiod was provided by fluorescent lamps. Images of ten plants were acquired every 10 minutes for 5 days and stored for later evaluation.
It was clear that hypocotyl elongation was enhanced as DIF increased and that DIF was effective in Brassica oleracea var. acephala. A characteristic elongation pattern was not observed for each DIF conditions during the light period. However, there were characteristic elongation patterns during the dark period, and remarkable elongation was found during the three hours immediately after the beginning of the dark period under the -10 DIF condition. In 0 and +10 DIF conditions,remarkable elongation occurred for four and nine hours starting one hour after on set of the dark period, respectively. These findings showed that the difference of hypocotyl elongation under DIF conditions occurred during the dark period, and it was found that elongation was particularly remarkable when the temperature during the dark period was low.
