Effect of End-of-day Heating Treatment on Floral Initiation and Development in Tagetes erecta

Abstract

We investigated the effects of short-term heat treatment during the dark period on early growth and flower initiation and development in African marigold (Tagetes erecta L.). Under a controlled cycle of a 12-h day length at 22°C/14°C (light/dark), the effects of heat treatment at 30°C for 3 h were tested at different time points during the dark period. We found that flower initiation and early flower bud development were accelerated at the beginning of the dark period, while early growth and flower bud development after flower budding were accelerated by heat treatment in both phases (end of day and end of night) of the dark period. Thus, with the analogy of end-of-day FR, we propose end-of-day heating, which involves short-term heat treatment at the beginning of the dark period, for accelerating flowering.