Ecological studies on the salad crops. I

Abstract

1. The effects of temperature, phtoperiod and gibberellin spray on developmental phases (bolting, budding and flowering) of head lettuce plants were observed. The plants were grown in the growth cabinet in which temperature and photoperiod was controlled strictly.2. All of the combinations of air temperature of 10, 15, 20 and 25°C with long and short day induced bolting in head lettuce.3. Bolting of head lettuce was more prevented under short than long day at the same treatments of temperature. Thus, the bolting of head lettuce was delayed by short day.4. Budding and flowering of head lettuce was more promoted under high temperature and long day than low temperature and short day. High temperature and long day accelerated budding and flowering in head lettuce.5. Bolting, budding and flowering of head lettuce were more promoted under high temperature and long day than low temperature and short day.6. The effects of gibberellin on the reproductive phase of head lettuce treated at 10°C, as influenced by photoperiod are recorded in Figure 3 and illustrated in Figure 4. No significant differences were observed between gibberellin treated plants and non-treated plants in flowering date.Gibberellin promoted bolting in head lettuce grown under short and long day, but it failed to hasten budding time of head lettuce.7. The favorable conditions of temperature for fertility were from 15 to 20°C. The plants treated at 25°C fertilized slightly. In contrast, the plants treated at 10°C under both photoperiods resulted in sterility without normal flowering.These results suggested that critical evaluation of low temperature to fertility was the range of 10 to 15°C.8. The favorable conditions of temperature to growth responses of head lettuce were from 15 to 20°C.The number of leaves and branches was higher under conditions of high temperature and short day than low temperature and long day.Green color of the leaf under conditions of low temperature and long day was deeper than that under high temperature and short day.