<i>Clivia miniata</i> REGEL (ウケザキクンシラン) の開花に及ぼす温度効果

Abstract

Clivia miniata, native to Natal, is one of the valuable flowering pot plants in Japan. The plants are usually grown under glass during winter months and produce flowers in April. When the room temperature is raised by over-heating, they fail to produce flowers. It is known by our previous study that the flower initiation occurs in April and all florets in an inflorescence develop to the carpel primordia forming stage in October, but the flower do not unfold until the following Spring.The authors assumed that the plant requires a certain duration of low temperature after that stage in order to elongate its scape and to produce normal flower.The present study was conducted to clarify the effect of low temperature given after the completion of the floral organs on successive flowering.1. When a plant was kept above 20°C continuously, the plant failed in the emergence of flower bud. Good flowering was obtained when a plant had received 50 days of natural cold under frost protection from the middle of January and again transferred to warm temperature above 20°C. The cumulative hours below 10°C during this cold period amounted approximately to 1, 000 hours.2. In orders to determine the critical temperature for the chilling effect, plants were treated with constant temperature of 10°, 15° or 20°C for 60 days from the latter part of October and then were shifted to above 20°C. As a result, scape elongation and normal flowering were observed in plants treated at 10°C and not in those treated at 15°C. However, when the duration was shorter than 45 days, the chilling effects were insufficient even in the treatment at 10°C.3. Insufficient chilling, either by imperfect degree or duration of cold, brought a check of scape elongation and, as the result, anthesis occurred in the low position being surrounded by the whorl of foliage leaves.4. After the chilling requirement was fully satisfied and the flower bud just emerged, warm temperature promoted the subsequent flowering. Long days by supplemental lighting after shifting to warm temperature showed the compensatory effect for the insufficient chilling.5. With the object to force the plant for Christmas flowering, chilling treatments at 10°C for 60 days beginning from August 20 and September 20 were given. The treatment from August 20 showed little effect on the flower development, whereas the treatments from September 20 brought a favourable effect and enabled to produce flower in Christmas. Treatment at 6°C in continuous darkness gave the similar effect as treatment at 10°C under light.