Depth of Dormancy and Response to Chilling in Freesia Corms

Abstract

Freesia corms were either subjected to smoke or ethylene to break dormancy, and the corms were stored dry at room temperatures following the treatment. For the determination of depth of dormancy, they were planted at different times for the sprouting test. The differentiation of leaves on their uppermost axillary buds and formation of roots on their basal parts were also observed. To determine the chilling response, the treated and non-treated corms were transferred to wet cool storage at 10°C for 5 weeks at different times, and later planted in pots and grown.
Non-treated corms showed resumption of leaf differentiation on their uppermost buds followed by root formation and rapid sprouting after planting on August 31, while ethylene or smoke pre-treated corms attained the same state on August 17 or July 20, respectively, i. e. 2 or 6 weeks earlier. This fact demonstrates the promotive effect of smoke or ethylene on the breaking of dormancy.
At the end of chilling, sprouting and differentiation of flower-buds were most advanced in the smoke-treated corms, followed by ethylene-treated ones, and then by non-treated ones. When smoke or ethylene treated corms were transferred to the chilling on August 17 or August 31, respectively, they all flowered and exhibited full chilling response. On the other hand, only 86% of the non-treated corms flowered even when they were chilled on September 14.
Full chilling response was obtained when corms were chilled after roots appeared on their basal parts. Thus, root formation is a good indicator of the starting time of chilling.