Studies on the high temperature treatments of the bulbs to blindstoken in tulips. (II)

Relation between the degree of injury in the flower bud and the yield of new bulbs

Abstract

In the previous paper, the authors reported that the high temperature treatment of the bulbs was effective for increasing the yield of new bulbs, and the effectiveness depended on the date and length of the treatment, or the degree of injury in the flower bud by the treatment. In this study, the authors carried out two experiments to clarify the relation between the degree of injury in the flower bud and the subsequent growth and yield of new bulbs.
In the first experiment, the bulbs of Bartigon variety were treated at 33°C for 8, 12, 16, 18, 20 or 23 days from Oct. 7. In the second experiment, bulbs of City of Haarlem variety were treated at 33°C, for 24 days from Sept. 15, for 17 days from Sept. 30, or for 8 days from Oct. 17. A few bulbs had been taken out at intervals during the treat-ment, and the grade of injury in the flower buds by the treatment was examined.
The degrees of injury in the flower bud were, classified into the following five grades.
0: no injury.
1: the tips of the petals were slightly softened.
2: about one third of the petals was softened and membranous, and stamens started to be softened.
3: about a half of the petals was membranous, and the stamens were perfectly softened.
4: petals turned to be perfectly membranous, and both stamens and pistil were softened.
Young leaves and flower stem were not injured, even if the flower bud was perfectly softened. But they were likely to be softened when the bulbs were treated so drastically as the flower bud turned brown.
The highest yield of new bulbs was obtained, when the effect of the treatment was high enough the degree of injury in the flower bud was advanced to the 2 or 3 grade.
From the practical stand point, it is suggested that grade of injury in the bulb may be exactly deter-mined by examining a few bulbs at intervals until the proper grade is attained.