PHYSIOLOGY OF DORMANCY IN TROPICAL GEOPHYTES

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Physiology on dormancy in geophytes of tropical origin were studied.Cold treatment is a common method for forcing Hippeastrum, but the role of the low temperature is not understood. In Hippeastrum, flower but development in the bulbs grown at 25ﾟC were observed throughout a year. Low temperature did not accelerate flower development, but maintained flower buds grow healthy and preveny from aborting. Relationship between ABA fluctuation and flower development during storage was clarified. An important role of basal plate in twin-scale propagation was also clarified.Tubers of Gloriosa did not have any dormancy when planted without dividing a set of two tubers into two independent tubers, whereas those divided had a dormancy. Ascisic acid and indole-3-acetic acid were the major controlling factor for sprouting.Cold treatment to the corms of tuberose is a practice of retarded flowering. In this study, it is clarified that low temperature storage has almost no advantage for flowering at a desired time. The corms can be stored at higher temperatures as 20 to 25ﾟC after harvesting until planting. Endogenous gibberellins increased in the corms during cold treatment, but had no role on elongation growth thereafter.