Responses of fall-flowering chrysanthemum varieties to photoperiod and temperature (I)

1. Expriments were conducted with 17 varieties of fall-flowering chrysanthemum on their sensitivity to photoperiod and temperature in 1952. They were grown in the two localities (Nagano, 360m and Osamura, 850m above the sea-level) having different temperature conditions, and under short day of 10 hours for 20 or 30 days, or under natural day-length.2. Three out of 19 varieties tested, Tatsunami, Shinanogawa and Hakuba, differentiated flower bud at the same time irrespective of photoperiod. Another 14 varieties differentiated flower bud when day length had been reduced to 14.5 hours. Time of flower bud differentiation in Shintoa, Pinktoa, Shingetsuyu and Minori, was somewhat earlier than that of the other varieties.3. Development of flower bud in the three varieties, Tatsunami, Shinaogawa, and Hakuba, was not affected by photoperiod, but only by temperature ; temperature the cooler, flowering the later.In another 14 varieties, development of flower bud was affected by photoperiod and temperature. Flower bud developed when daylength had been reduced to 13.5 hours. In the four varieties, Shintoa, Pinktoa, Shingetsuyu and Minori, bud development was not retarded by higher temperature, while in other ten varieties, Okayamaheiwa, Ruster, H. Koido, Shirasagi, Murakumo, Tamaorihime, Kuninohikari, Benishio, Beniaki and Hatsugasumi, it was retarded by higher temperature even under short day condition.4. In 20 days' treatment of shading (10 hours photoperiod), there appeared many crown bud resulting from imperfect flower bud development. No variety formed perfect flower by such a short treatment. In 30 days' treatment, stages of flower bud development affected the appearence of crown bud, which was influenced by both factors.5. Earliness of flowering was determined only by the temperature conditions in the varieties of temperature sensitive type. With the varieties, which were sensitive to both temperature and photoperiod, earliness of flowering was determined by the length of time from bud differentiation to flowering. In practical shade culture it should be recommended to use the varieties which need relatively short period from the start of treatment to flowering.6. Chrysanthemum varieties tested were classified in the following groups in relation to their responses to temperature and photoperiod.a. Flowering was influenced only by temperature: Tatsunami, Shinanogawa, Hakuba.b. Flowering was influenced mainly by daylength (flower bud differentiated when daylength had been reduced to 14.5 hours, flower bud developed when daylength had been reduced to 13.5 hours).i. Flowering was forced by rather higher temperature; Shintoa, Pinktoa, Minori, Shingetsuyu.ii. Flowering was retarded by higher temperature: Okayamaheiwa, Ruster, H. Koido, Shirasagi, Murakumo, Hatsugasumi, Tamaorihime, Kuninohikari, Benishio, Beniaki.