Lily bulblets produced in tissue culture at 20 or 25ºC are cold-treated before planting to break dormancy. Bulblets produced in tissue culture at a relatively low temperature (15ºC), though, are nondormant and sprout without a preceding cold treatment. Leaves generated after planting by noncold-treated 15ºC bulblets, were relatively small and as a consequence bulblet growth after planting was limited. This was also observed for the few 20 and 25ºC bulblets that did sprout without a cold treatment. Sink-strength of bulblets was assessed as bulblet dry-weight (DW) gain per mg leaf DW. Noncold-treated bulblets had far less sink-strength than cold-treated ones. Thus, a second cause of the little growth of noncold-treated bulblets was their small sink-strength. The optimal temperatures to break dormancy and to promote sink strength were 9 and 2ºC, respectively. It is concluded that a cold treatment not only breaks dormancy but also enhances sink strength, and that these are unrelated processes.
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