On the Rosetting of Chrysanthemum Plants

Effects of Cutting Time and Low-temperature Treatment of Rooted Cuttings on Stem Elongation and Leaf Number in Cultivars of Chrysanthemum morifolium Ramat.

“…In the present study, it was established that a constant night temperature of 12.5°C (19:00-7:00) reduced the internode length or induced rosette formation in rooted cuttings taken from mother plants exposed to high temperatures for an extended period and subsequently exposed to low temperatures less than 15°C in accordance with the findings of Konishi (1980). Regarding the relationship between the date on which cuttings were taken from mother plants and ISL of the rooted cuttings, the ten cultivars used in the experiments could be divided into three groups based on ISL ratios of rooted cuttings propagated in late-September, midNovember, and mid-December.…”

“…The factors responsible for rosette induction and the degree of low temperature exposure required to break the rosette stage seem to vary between cultivars (Okada, 1959). The Japanese cultivars 'Okayama Heiwa', 'Shinn Toa', 'Uchusen', and 'Tama Orihime', in which environmental factors inducing rosette formation have been investigated previously, formed rosettes readily in autumn and winter (Konishi, 1975(Konishi, , 1980Okada, 1963).…”

“…From the results above, the stem elongation ability of Japanese autumn-flowering cultivars is considered to be reduced by either of two types of temperature-related factors; high temperature plus subsequent low temperature below 15°C, as Konishi (1980) described; or high temperature only or high temperature plus a subsequent short period of low temperature. The rosette-type development of shoots was recovered by lowtemperature treatment of rooted cuttings taken from mother plants in September to October.…”

“…These mother plants did not always exhibit typical rosette formation, and internodes of the lateral shoots slowly elongated in midNovember at a low temperature below 10°C in a plastic greenhouse, whereas only mother plants of 'Shuho no Chikara' formed perfect rosettes. It is considered that the first group of cultivars may belong to the type of cultivars that Okada (1959) and Konishi (1975Konishi ( , 1980 investigated. The capability for stem elongation in these cultivars might be lowest at around mid-November when mother plants were exposed to extended high temperature and subsequently exposed to low temperature below 15°C.…”

“…These findings indicate that Japanese autumn-flowering cultivars show a rosette tendency (expressing characteristics of a rosette stage) to varying degrees, and the reduction of stem length and leaf number of rooted cuttings taken from mother plants in late summer and autumn vary by cultivar. Thus, it is necessary to reconsider the characteristics of Japanese autumn-flowering cultivars that Okada (1959Okada ( , 1963 and Konishi (1980) reported previously. In the study, we elucidated the effects of cutting time from mother plants and low-temperature treatment of rooted cuttings on stem length and leafing in ten autumn-flowering cultivars and evaluated the capability of stem elongation of these cultivars.…”