Responses of fall-flowering chrysanthemum varieties to photoperiod and temperature (2)

Abstract

(1) Experiments were conducted with 16 varie-ties of fall flowering chrysanthemum on their sensi-tivity to photoperiod and temperature in 1953. 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 days or until flowering period, or under natural daylength. (2) Five out of 16 varieties tested, Hatsunishiki, Harukoma, Shochiku, Hitomesenryo and Hoyoku, differentiated flower bud at the same time irre-spective of photoperiod. Another 11 varieties differentiated flower bud when daylength had been reduced to below 14.5 hours. Time of flower bud differentiation in Shintoa, Ayamurasaki and Shiki-nohikari was somewhat earlier than that of the other varieties. (3) Development of flower bud in the five var-ieties, Hatsunishiki, Harukoma, Sh6chiku, Hitome-senryo and Hoyoku was not affected by photoperiod, but for the most part by temperature; temperature the cooler, flowering the later. In another 11 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, Ayamurasaki, Shikinohikari, and Shikinomidori, bud development was not retarded by higher temperature, while in other seven varieties, Kyowashiro, Renzannotsuki, Shuho, Sakuranohikari, Kurokoma, Hoen and Shin-ginga, it was retarded by higher temperature even, under the short day condition. (4) When influenced by extreme variation on daylength and temperature conditions before the differentiation of floret primordium, there appeared many crown buds resulting from imperfect flower bud development. (5) The chrysanthemum varieties tested were classified in the following groups in relation to their responses to temperature and photoperiod. A. Flowering was influenced mainly by temper-ature ature: Hatsunishiki, Harukoma, Shochiku, Hitome senryo, Hoyoku. B. Flowering was influenced mainly by daylengtft (flower bud differentiated when daylength had beenn reduced to 14.5 hours, flower bud developed when daylength had been reduced to 13.5 hours or less), (a) Flowering was forced by rather higher temper-ature; Shintoa, Ayamurasaki, Shikinohikari, Shikinomidori. (b) Flowering was retarded by higher temper-ature; Kyowashiro, Renzannotsuki, Shuho, Sakurano-hikari, Kurokoma, Hoen and Shinginga.