Survival of cryopreserved shoot tips of papaya (Carica papaya L.) exposed to various pretreatments

• Main Authors: Ju, Lih-Shuwn, 朱麗淑
• Other Authors: Song-Iuan Liaw
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/16119697900579730465

碩士 === 國立中興大學 === 植物學系 === 85 === Abstract This study used tissue cultured plantlets of papaya ( Carica papaya L. cv. Tainung No2. ) as materials for investigation. The main purpose is to investigate the survival ratio of the shoot tips under various pretreatments after cryopreservation. To understand the degree of damage to the overall physiology performance of papaya, MDA production of shoot tips wasmeasured to indicate the effect of cryopreservation on cell membrane, as well as the photosynthetic rate of the leaves. Survival of cryopreserved shoot tips of papaya did not increase when tissue cultured papayas was pretreated with ABA ( 100mm abscisic acid ) and different low temperatures treatment ( 20℃、15℃、10℃ ). After plantlets were grown in hardening media supplemented with 0.5 M sucrose for a week, the shoot tips were excised, dehydrated for 20 mins, transferred to cryotubes and plunged directly into liquid nitrogen for storage. After 24 hr, frozen shoot tips were thawed at 40℃for 1 min and then transferred to regrowth media. The survival of shoot tips was up to 60%. In another experiment, tissue cultured plantlets were grown in standard hardening media for a week, the shoot tips were excised, dehydrated for 40 mins, treated with different cryoprotectants by shaking for 1 hr, transferred to cryotubes and cooled at 1℃per minute to -40℃, and then plunged into liquid nitrogen. After 24hr, frozen shoot tips were thawed at 40℃for 1min and then transferred to regrowth media. The survival of shoot tips was up to 77.8%. The damage of membrane in shoot tips was measured as MDA production from various procedures of cryopreservation. Application of cryoprotectants increased the amounts of MDA synthesized,which is higher than other treatments. These results suggest that cryoprotectants have positive effect on lipid peroxidation of cell membrane. Moreover, sucrose was the most effective one among those cryoprotectants. As the results show, the concentration of sucrose used in this experiment may be too high for papaya shoot tips, therefore it caused osmotic stress, resulting in lipid peroxidation of cell membrane. The effects of various cryoprotectants on leaf photosynthetic rates were also measured. Photosynthetic rates decreased with increasing the concentrations of ethylene glycol, dimethyl sulfoxide and glycerol. However, certain ranges of sorbitol, polyethylenglycol, sucrose and proline caused increased photosynthetic rates. Here we concluded that selecting of suitable compositions and concentrations of cryoprotectants is a major factor for cryopreserving papaya shoot tips.