This experiment was carried out to clarify the effect of the high temperature treatment on the new bulb formation and development in tulip bulbs, and to find out the most desirable degree of injury in flower bud for getting the high yield of the new bulbs.
The bulbs were treated at 35°C before planting. The varieties used were Feu Brilliant and William Copeland. The plants dug up at the end of the growing season, and the relation between the development of the floral and vegetative organs and the number and yield of the new bulds was studied.
The plants which had developed flower stalks and flower buds, but had not bloomed, produced highest yield: 23_??_30 percent increase over that of the control plants. The plants, which developed flower stalks, but not flower buds, got largest number of new bulbs, 20_??_26 percent over the control, but their weight was not so high as in the plants above mentioned. The plants which failed to develop flower stalks porduced poor yield of new bulbs.
The central nose was most sensitive to the treatment. When the treatment was given, the flower bud was affected at first, and as the length of the treatment was prolonged, flower stalk and vegetative organs became to be affected successively. When the flower bud was slightly injured, the growth of the ventral bud and offsets was accelerated and the yield of the new bulbs was increased. When the treatment was drastic enough to injure other parts, new growth was retarded and the yield was reduced. The most desirable degree of the treatment was long enough to make the flower bud fail to open, but not to affect furthermore. In this case, highest increase of yield of new bulbs is expected over that of the control.