EFFECT OF STORAGE TEMPERATURE ON DORMANCY AND SPROUTING IN DUTCH IRIS BULBS

Abstract

1) Dutch iris bulbs (cv. Wedgwood) stored at 13, 8 or 2°C for about four months just after harvest and planted at the experimental farm at the end of September showed dormancy, while those stored at 17 or 30°C exhibited normal growth.2) Bulbs stored at 20°C from the beginning of June showed a rapid increase in the length of the first leaf after the beginning of August, while those stored at 10°C remained in a state of rest and initiated new bulbs inside the mother bulbs. This phenomenon is quite similar to pupation of freesia corm.3) The higher the temperature and the longer the duration of the curing period, the higher the percentage of sprouting among lots exposed to 20, 25, 30 or 35°C.4) Heat curing at 30°C was slightly more effective than that at 20°C for six week storage periods after harvest. However, heat curing at 30°C was less effective than that at 20°C, if the curing period was prolonged for more than 8 weeks.5) A larger heat sum is necessary for flowering in forcing than is needed for sprouting. Bulbs stored at 20°C from June 9 required about 40 days prior to cooling at 8°C for 49 days for a high percentage of flowering.6) Application of regulators (benzyladenine, gibberellin and ethephon) were examined for their effects on the sprouting of bulbs. There was no difference between treatments with benzyladenine or gibberellin given prior to or after heat curing, while ethephon was only effective when given after heat curing.