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Study of pretreatments for cryopreservation of sweet potato
|摘要:||甘藷（sweet potato；Ipomoea batatas（L）Lam.）為熱帶作物，由於具有不耐低溫之生理特性，故無法以冷馴化的方式，誘導其產生耐寒性與耐旱性。為了達到超低溫冷凍保存之目的，以0.3 M蔗糖進行前處理，藉由適度的滲透逆境，誘導植株產生耐寒性與耐旱性。
台農68品系甘藷，以株齡80天之植株為材料，進行0.3 M蔗糖前處理7天，配合LS處理60分鐘，PVS2處理55分鐘，超低溫冷凍保存後，可達到22.2 % 之存活率。台農57品系甘藷，以株齡40天之植株為材料，進行0.3 M蔗糖前處理3天，配合LS處理60分鐘，PVS2處理35至55分鐘，超低溫冷凍保存後，可達到87.5至100 % 之存活率。
為了解影響甘藷超低溫冷凍保存存活率之主要因素，將不同株齡之植株處理0.3 M蔗糖不同天數，進行相對含水量、滲透潛勢、可溶性醣類與可溶性蛋白質含量之測定。發現可溶性醣類含量為影響滲透潛勢變化之主要因素，而當可溶性醣類含量與滲透潛勢具有高相關時，超低溫冷凍保存存活率則較高。另外也發現，在滲透逆境下，滲透潛勢下降幅度愈大、下降速度愈快且愈持久時，超低溫冷凍保存存活率亦較高。藉由上述結果，推測0.3 M蔗糖處理1至7天，為較佳冷凍保存處理天數。亦推測年輕植株之莖頂較成熟植株更適合進行超低溫冷凍保存之處理。而在滲透逆境下，累積的可溶性醣類主要為雙醣且具足夠累積含量時，亦可達到較高之超低溫冷凍保存存活率。|
Sweet potato(Ipomoea batatas(L)Lam.)is a tropical plant which is unable to be cold-hardened. To achieve cryopreservation of this plant, We have used osmotic stress to replace the treatment of low temperatures. Suitable osmotic stress induced by 0.3 M sucrose preculture is aimed at enhancing the tolerance to desiccation and freezing of this plant to be cryopreserved. The shoot tips of sweet potato TN68(Ipomoea batatas(L)Lam. cv. Tainung No. 68)were excised from 80-day-old in vitro-grown plantlets and pretreated on solidified MS basal medium supplemented with 0.3 M sucrose for 7 days. The precultured shoot tips were treated with a loading solution(LS)for 60 minutes and then dehydrated with a vitrification solution(PVS2)for 55 minutes prior to a plunge into liquid nitrogen. The post-thaw survival rate of shoot tips was up to 22.2 % . The shoot tips of sweet potato TN57(Ipomoea batatas(L)Lam. cv. Tainung No. 57)were excised from 40-day-old in vitro-grown plantlets and pretreated on solidified MS basal medium supplemented with 0.3 M sucrose for 3 days. The precultured shoot tips were treated with a loading solution(LS)for 60 minutes and then dehydrated with a vitrification solution(PVS2)for 35-75 minutes prior to a plunge into liquid nitrogen. The post-thaw survival rates of shoot tips was up to 87.5-100 % . To understand the action of sucrose in conferring desiccation and freezing tolerance, we analyzed the hydric and biochemical modification in pretreated plantlets. The results indicated that the accumulation of soluble sugar was the main effect that leaded to the decrease of osmotic potential. When the correlation of soluble sugar content and osmotic potential was high, the survival rate of cryopreservation was also high. When the decrease of osmotic potential was large and more rapid and lasting, the survival of cryopreservation was also better. Based on the results shown above, the best pretreatment time was 1-7 days and the shoot tips from young plantlets was better than old plantlets for cryopreservation. What kinds of soluble sugars accumulate after osmotic stress is important. We found that the accumulation of disaccharide can make the survival of cryopreservation to be better.
|Appears in Collections:||生命科學系所|
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