Night temperature determines flowering time and quality of Chrysanthemum morifolium during a high day temperature

摘要

The effects of controlling night temperatures (NTs) during summer-season on flowering and photosynthetic characteristics in Chrysanthemum morifolium were investigated at NTs of 20, 23, 26, or 29 degrees C and a day temperature (DT) of 35 degrees C. Days to budding and flowering increased more in the plants grown at NTs of 26 or 29 degrees C than those of 20 or 23 degrees C, regardless of cultivar. The flowers appeared as a withered state in 'Swifty Rosso' grown at a 26 degrees C NT and 'Swifty Yellow' at 26 or 29 degrees C NTs. The percentage of abnormal flowers reached 100% in 'Swifty Rosso' grown at a 26 degrees C NT and 26 and 29 degrees C NTs in 'Swifty Yellow'. Flower size were the largest in the plants grown at 20 or 23 degrees C NTs than those at 26 and 29 degrees C NTs. The net CO2 assimilation rates had average high values in the plants grown at 20 or 23 degrees C NTs. Low photosynthetic efficiency was found in the plants grown at 26 or 29 degrees C NTs. At the high DT that occurs during the summer season with high NTs >= 26 degrees C delays budding and causes abnormal and withered flowering. Since it is year-around plant, techniques of controlling NTs can be used effectively while maintaining quality levels.