Abstract
Marguerite plants were propagated at every about a month, and the rooted cuttings were planted in the unheated greenhouse. Five days after planting each plant was received a single pinch, and the pinching was done at intervals of 30 days from January 1, 1971. Thus the seasonal change of flowering response in marguerite was investigated. The formation of flower bud was observed anatomically, and the effect of high temperature on flower initiation was also studied. Furthermore, the effects of daylength, low temperature treatmemt at the early stage of growth, and growth temperature of stock plants on flowering were studied.
The results obtained were as follows:
1. The flowering response in marguerite changed seasonally. When the plants were pinched prior to late May and were grown in the spring and early summer, they flowered sooner and with fewer leaves. Plants pinched on June 30 were retarded to flower and their leaf numbers below the inflorescences extremely increased. After then, the later the pinching time, the sooner the plants flowered.
2. Under the favorable conditions, marguerite plants initiated flower buds immediately after the pinching time, and budded within 20 days.
3. The flower initiation was perfectly prevented by the temperatures higher than 20°C of daily minimum. These high temperatures, however, did not inhibit the development of flower bud.
4. When the plants were grown under the high temperature conditions for longer period, not only the flower initiation was prevented, but also the phenomenon like devernalization took place, and the plants became hard to flower.
5. When those plants hard to flower were treated with low temperature, they became easy to flower again.
6. The long photoperiods promoted the flower initiation in marguerite.
7. The flowering response in marguerite changed seasonally even when the plants were grown at 15°C throughout the year. Thus the endogenous rhythm in flowering response of marguerite was observed.
