Effect of Temperature on the Flower Bud Formation in Iris ′Wedgwood′
1974 Volume 43 Issue 1 Pages 84-90
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1974 Volume 43 Issue 1 Pages 84-90
In order to examine the effect of low temperature on flower bud formation, bulbs of iris‘Wedgwood’were stored at low temperature of 8°C or 13°C for 35 days from August 12 and then shifted to 15°C, 20°C or 30°C. Flower bud formation was most promoted in the bulbs stored at 13°C followed by 15°C, at 8°C followed by 15°C, at 8°C followed by 20°C and at 13°C followed by 20°C in the succeeding order. Bulbs shifted to 30°C after the low temperature storage did not initiate flower buds, but were in rest. On the other hand, flower bud formation was occurred after long termes of period in the bulbs which were not exposed to the low temperature and kept at continuous 20°C. More leaves were formed before flower bud formation in the bulbs stored at 13°C than in those stored at 8°C. Longer first leaf was obtained at 20°C than 15°C and 13°C than 8°C, whereas leaf elongation was restricted at 30°C.
Flower bud formation was not promoted by pretreatment of high temperature at 30°C or 35°C for 13 days from August 9 to 22, just before the low temperature treatment, but rather delayed compared with no pretreatment.
In the bulbs treated at 10°C for 45 days, flower bud initiation was delayed by the treatment with high temperature at 35°C for the following 16 days, but not delayed by the treatment for 2, 4 or 8 days. In the cese of storage at 10°C for 30 days, it was delayed by the treatment for 8 or 16 days, but not by the treatment for 2 or 4 days. The length of period delayed, however, was nearly the same as the duration of high temperature treatment in both cases.
The conclusion that the low temperature not only induces directly the flower bud initiation, but accelerates afterwards the flowering during forcing period, may be drawn based on the results obtained. The flower bud initiation was delayed by high temperature after low temperature treatment when the latter was incomplete or the former was long enough. The effect of high temperature, however, was not so remarkable.
