Rosetting Prevention in Chrysanthemum by Chilling the Rooted Cuttings

Abstract

The effects of the cold storage of rooted cuttings which had not yet assumed the rosette form, and the effects of growth temperature on stem elongation and flowering in chrysanthemum were studied.
In Experiment 1 the rooted cuttings of cv. ‘Okayamaheiwa’ which had been stored at 1-3°C for 0, 10, 20, and 40 days were planted in a heated greenhouse on Nov. 30, and were grown under long-day conditions. After 10 days they were pinched and transferred to short-day conditions. On the same day night temperature treatments of 5, 10, 15, and 20°C were initiated.
Under low night temperature conditions, plants unchilled or chilled for shorter periods assumed the rosette form, while those chilled for longer periods elongated and flowered well. Under high temperature conditions, however, the unchilled plants elongated and flowered as well as those chilled for longer periods.
In Experiment 2, the pinched rooted cuttings of cvs. ‘Uchusen’ and ‘Tamaorihime’ were stored at 1-3°C for 40 days, and planted with the unchilled cuttings in the heated greenhouse under long-day conditionson, on Nov. 16. After 20 days they were transferred to short-day conditions and night temperature treatments of 5, 10, 15, and 20°C were initiated. The results obtained were essentially the same asin Experiment 1.
These results show that the growth activity of the chrysanthemum plant becomes lower during the winter season, and the temperature range within which the plant can elongate is narrow. A plant in this state can elongate and flower nly at higher temperatures. When the plant is exposed to low temperatures, its growth activity is increased. Thus the plants exposed to low temperatures elongate and flower at lower temperatures as well as at higher ones.