| Summary: | 碩士 === 國立中興大學 === 植物學系 === 88 === Abstract
In vitro plantlets of three yam species were subjected to a wide range of preculture condition (high sucrose , cold hardening ,short photoperiod , ABA and growth retarding agents) and different cryopreservative treatments (vitrification, cryoprotective-dehydration and encapsulation-dehydration) were used for cryopreservation technique.
According to the results, among these three species, D.alata L.var.purea (Roxb.) M. Pouch was the most tolerant one to cryoprotectant and D.doryophora Hance had higher dehydration tolerance than other two species. Several pre-treatments tested, such as cold hardening and short photoperiod preculture for 1-3 weeks, 100μM ABA preculture for 1-3 days, growth retarding agent CCC at 0.025μM,0.05μM and 0.1μM or B995 at 1μM,2μM and 4μM preculture for 2 weeks, did not enhance the tolerance to freezing in three yams. Preculturing in the medium containing 0.75M sucrose for 10 days can induce the resistance to desiccation and to freezing in the liquid nitrogen of D.doryophora Hance .
All three species of yam were cryopreserved by vitrification protocol, but they did not survive after freezing- thawing. D.doryophora Hance was precultured with 0.75M sucrose and dehydrated in silica gels for 90 min and the results showed 30% of survival rate. The highest survival rate (33.33%) was achieved by using encapsulation-dehydration protocol. We found that after one to three months subculturing, yam can survive after cryopreserved. Besides, we also found if alginate beads were shaken in medium with high sucrose for 3 days, the chemical properties of alginate beads changed. We suggested that the change occurred in alginate beads can reduce serious dehydration damage caused by freezing — thawing process on yam. Therefore, yams can survive after cryopreservation.
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