Ranunculus asiaticus (L.) is an ornamental geophyte prized for its showy flowers and desiccation tolerant, dry TRs. R. asiaticus is native to the eastern Mediterranean in areas with a cool, wet winter and hot, dry summer. In their native and similar climates, the plants are commonly grown in the field for one or more seasons before the TRs are harvested, dried, and sold to flower growers worldwide. Although R. asiaticus grown from transplanted dry TRs reportedly produce a faster and more profuse flowering crop than when grown from seed (Meynet, 1993), inconsistent sprouting, poor uniformity, and abnormal growth habit are common problems after storage (M.A. Mellano, personal communication).
The influence of temperature and relative humidity on the aging of seeds has been well documented (Justice and Bass, 1978). The general recommendation is that the drier and cooler the storage environment, the longer seeds retain the ability to germinate (Priestley, 1986). Analogies are made throughout this article on seed storage as a well-studied system for low temperature and low moisture content storage. In this article, “seed storage” is for those species with orthodox storage behavior, those that can withstand desiccation (Copeland and McDonald, 2001).
Artificial aging of seeds has been recognized as a useful predictor of storability; those with reduced vigor under accelerated aging treatments usually respond similarly under long-term open storage (Priestley, 1986). In accelerated aging experiments, seeds are stored much warmer than is typical, at 35 to 45 °C, and up to 100% relative humidity, which lowers viability in seeds in a matter of days or weeks as compared with years in naturally aging tissues (Bewley and Black, 1994). Traditionally, R. asiaticus dry TRs are handled by distributors who market other ornamental geophytes and typically have limited storage options at their disposal. These conditions are commonly cool and moist, appropriate for (Lilium spp. L.) bulbs; cool and dry such as with gladiolus (Gladiolus spp. L.); or room temperature and dry along with other dry-packed bulbs such as calla lilies (Zantedeschia sp. Koch.). Meynet (1993) suggested that R. asiaticus TRs should be stored at 15 to 25 °C and 50% relative humidity, which is common in the industry (M.A. Mellano and Y. Liberman, personal communication), but this range has not been scientifically tested. It is unclear which of the previously mentioned storage conditions are most appropriate for long-term R. asiaticus storage. The purpose of this research was to develop a storage protocol for R. asiaticus dried TRs by testing a range of storage moistures and temperatures and observing the influence on respiration and subsequent growth.
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