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Night temperature controlling for flowering in Chrysanthemum morifolium under high day temperature condition

ISHS Secretariat
Night temperature controlling for flowering in Chrysanthemum morifolium under high day temperature condition

I’m a PhD student in the Department of Horticulture, Biotechnology and Landscape Architecture at Seoul Women’s University, Republic of Korea. I finished my BSc in 2016 and completed my MSc in 2018 at Seoul Women’s University. My dissertation research project is focused on growth and flowering of orchid plants in response to elevated CO2. My objective was to study carbon reduction by controlling night temperature (NT) to save cooling expense during high daytime temperature (DT). I selected Chrysanthemum morifolium as the plant to be studied. This Chrysanthemum is a widely used ornamental for cut flowers or containerized plants. This ornamental is produced year-round throughout the world. Because the number of extreme summer temperature events has increased markedly, cooling systems are required for chrysanthemum cultivation during the summer season. Two cultivars of Chrysanthemum morifolium, ‘Swifty Rosso’ and ‘Swifty Yellow’, were grown in a plant growth chamber with NT of 20, 23, 26, and 29°C and DT of 35°C with 8 h photoperiod. As a result, the flowering quality (i.e., flower and ray floret size) was increased in the plants grown at NT of 20 and 23°C compared to those of 26 and 29°C, regardless of the cultivar. Time to flowering was fastened in the plants grown at NT of 20 and 23°C in ‘Swifty Rosso’ and 20°C in ‘Swifty Yellow’, among the NT treatments with increasing flower production. High NT induced the flower abnormality of chrysanthemums. The percentage of abnormal flowers reached 100% in plants grown at NT of 26 and 29°C at 60 and 80 days after treatment (DAT), respectively, in ‘Swifty Rosso’. In ‘Swifty Yellow’, plants grown at NT of 26°C also reached 100% abnormality at 85 DAT and those of 29°C had not bloomed until 119 DAT. The highest ACO2 was found in the plants grown at NT of 20°C until 50 DAT in C. ‘Swifty Rosso’ and 23°C at 20 DAT in ‘Swifty Yellow’. These results indicate that decreased flowering quality (i.e., flowering delay, emergence of abnormal flowers, and decreasing photosynthesis) of chrysanthemum under high DT can be resolved by NT control. NT under high DT should be controlled below 23°C to produce high-quality containerized plants of Chrysanthemum morifolium ‘Swifty Rosso’ and ‘Swifty Yellow’.

Ah Ram Cho won the ISHS Young Minds Award for the best poster presentation at the the III International Symposium on Germplasm of Ornamentals in the Republic of Korea in October 2020.

Ah Ram Cho, Department of Horticulture, Biotechnology and Landscape Architecture, Seoul Women's University, 01797 Seoul, Republic of Korea, e-mail: ar092@swu.ac.kr

The article is available in Chronica Horticulturae

Chrysanthemum morifolium
Young Minds Award Winners