Application of photo-thermal models to quantify flowering time and development response of Chrysanthemum (Chrysanthemum × morifolium Ramat.)

Abstract: Chrysanthemum is a short-day plant, which flowers when the night length is longer. Photoperiod and temperature are two key environmental factors that affect time of flowering. In the current research, experiments were carried out to study the flowering response of two cultivars of chrysanthemum, i.e., Crimson Glory and Snowscape under four distinct photoperiods (8, 11, 14, and 17 h d^?1), shading levels (20, 30, 40, and 60%), and temperatures (10, 15, 20, and 25 °C). A qualitative short-day response was observed in all experiments. Both cultivars took minimum time to flower when grown under 8 h d^?1, however, it was significantly delayed when photoperiod decreased. Similarly, days taken to flowering were decreased significantly when plants were grown in 30% shade, which was delayed by increasing shade level (40 and 60%). Temperature also had a significant effect on the developmental phases of flower as above (25 °C) and below (10?15 °C) 20 °C temperature delayed flowering time. The present study also confirms that per day rate of progress to flowering was higher at 8 h d^?1 photoperiod, in 30% shade level, and at 20 °C temperature. These findings revealed a prospect of plant scheduling of the flowering time of chrysanthemum cultivars grown in long-day photoperiod to extend their marketing period, as the plants remains vegetative. A steady supply of this flowering annual can also be maintained in the market by growing them under different shades. The quality of plants would also benefit from an ideal growing temperature of between 15-20 °C.