A DIFFERENCE OF RESPONSE TO LOW TEMPERATURE BETWEEN CAULIFLOWER AND BROCCOLI

Extremely early cultivars of cauliflower formed curds during the chilling treatment at temperatures below 25°C for four weeks. So, these cultivars have a direct flowering response to low temperature (a direct character). On the other hand, early and the intermediate cultivars formed curds after they were exposed to a low temperature and then transferred to a relatively high temperature. It shows that their flowering is induced by the after-effect of low temperature (an inductive character). Inductive temperatures and duration for thermoinduction in these cultivars were temperatures below 15–20°C for four weeks and temperatures below 15°C for eight weeks, respectively. The duration of the juvenile phases of extremely early, early and intermediate cultivars were 4–5 weeks, 5–6 weeks and 8 weeks after seed germination, respectively.

Every cultivar of broccoli differring in the earliness of flower head formation had an inductive character in the flowering response to low temperature and formed flower heads at temperatures below 15°C independently of day-length. Extremely early, early and intermediate cultivars formed flower heads at 15°C for 3–4 weeks, 3–4 weeks and 6 weeks, respectively. The duration of the juvenile phase of extremely early, early and the intermediate cultivars was 3–5 weeks, 4–6 weeks and 5 weeks after seed germination, respectively.

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