Effect of storage temperatures of seed bulbs on the dropper formation in tulips

Abstract

The effect of storage temperatures on the dropper formation in tulips has been studied in relation to the period of storage and to the time of planting, with Darwin Hybrid tulip, cultivar Apeldoorn which has an obstinate characteristic to form droppers. The main conclusions are as follows:As for the period of storage, the formation of droppers is affected by the temperature after mid-September, but not affected by the temperature before that. In the range of tested temperatures up to 25°C, the higher the storage temperatures are, the more the dropper formation is inhibited. Although later planting inhibits the formation of droppers more than earlier planting when bulbs are stored at a high temperature, the time of planting has nearly no influence on the dropper formation of the bulbs stored at a low temperature. Under the natural conditions of the tulip belt in this country, the seed bulbs of strong dropper-forming nature will usually form droppers at high rates owing to the rapid fall of temperature from the beginning of October. However, even with the materials of the present study, which are very liable to form droppers, the formation of droppers is almost completely inhibited by storing the seed bulbs at 25°C and by delaying the time of planting till November 20.The degree of inhibition of the dropper formation coincides exactly with that of the retardation of the development of young bud in the bulb and of the early growth after planting. Therefore, it is considered that the retardation of early growth brings about the inhibition of dropper formation. Although the above-mentioned retardation of early growth is gradually lessened with the progress of growth, a little retardation of growth still remains even when the growth gets to its maximum. The foliage whose early growth is retarded, on the other hand, dies off somewhat later than that not retarded. In the result, the retardation of early growth shows little harmful effect on the ultimate yield of bulbs, and so it may be negligible compared to the merit in the inhibiting effect on the dropper formation.