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題 名 | The Effects of Intracellular Solute Concentration on Freezing Avoidance by Supercooling--A Theoretical Freezing Model for Woody Plant Cells=木本植物細胞抗凍模型理論之研究--胞液溶質濃度及過冷效應對抗凍之影響 |
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作 者 | 林中和; | 書刊名 | 中華林學季刊 |
卷 期 | 31:2=121 1998.06[民87.06] |
頁 次 | 頁131-140 |
分類號 | 436.182 |
關鍵詞 | 過冷; 醣; 凝固點降低; 差異熱能解析; 體積彈性衡量; Supercooling; Sugar; Melting point depression; DTA; Bulk modulus; |
語 文 | 英文(English) |
中文摘要 | 當木質部薄壁細胞暴露在凝固點(註)以下,冰結晶形成在細胞間隙,但細胞內 之水份則處於過冷(supercooled)狀態,此現象使細胞不致於凝固及壞死,即使溫度降至零下 38℃。由於細胞外冰結晶之水勢隨溫度降低而減少(Ψ□=1.16T(℃) Mpa),導致細胞脫水, 並造成胞液溶質濃度上升,進而降低了胞液之凝固點(Tm,註)及均質成冰核點(Homogeneous ice nucleation temperature, Th),此特性使許多木本植物能抵抗極低溫之逆境。 本實驗利用差異熱能解析(Differential Thermal Analysis, DTA)及乳漿溶液(Emulsion)技 術,使各溶液之凝固點及均質成冰核點之線性迴歸關係得以確定,並以實驗結果探討細胞內 不同溶質種類、濃度及細胞壁特性(Bulk modulus體積彈性衡量)之交互作用對木質部薄壁細 胞抗凍之影響。 實驗結果證明抗凍性較佳之溶質依次為果醣(Fructose, Th/Tm=2.951)、蜜三醣(Raffinose, Th/Tm=2.763)、葡萄醣(Glucose, Th/Tm=2.744)、蔗醣(Sucrose, Th/Tm=2.706)、甘油(Glycerol, Th/Tm=2.178),而細胞具有高濃度胞液及較低之胞壁體積彈性衡量則具有較低之均質成冰核 點,此導致較佳之抗凍效果。若彈性衡量(ε)小於最大容許量(ε□),則薄壁細胞之胞液可 免遭受凍結之可能。 註:凝固點在此指非均質成冰核點(Heterogeneous ice nucleation temerature),其值等於固 態溶液之熔點(i.e. Freezing point = Melting point, Tm)。 |
英文摘要 | The movement of water from woody plant cells to extracellular ice during freezing increases cell solute concentration. This lowers the melting point of the cellular solution and also its ice nucleation temperature. The latter effect lowers the temperature at which intracellular ice formation may occur and, thereby, enhance freezing avoidance by supercooling of cell water. The amount of cellular water lost during near-equilibrium freezing depends mainly on the cell solute concentration and the volumetric bluk modulus of elasticity of the cell wall. Differential thermal analysis was conducted on emulsions of aqueous solutions of fructose, glucose, glycerol, raffinose and sucrose to measure the effect of solute concentration and solute type on the homogenous ice nucleation temperature. The nucleatin temperature was lowered by 2.951, 2.744, 2.178, 2.763 and 2.706 times the melting point depression in ℃ for each respective solute. The homogeneous ice nucleation temperature of distilled water was measured to be -38.7℃. These data were incorporated into a woody plant cell freezing model to predict the influence of solute concentration, solute type, and bulk modulus on intracellular freezing. Results of this analysis suggest that cells with a high solute content, solutes that have a large effect on the homogeneous ice nucleation temperature, and cell walls of low bulk moduli will display an enhanced avoidance of freezing by supercooling. Running title: FREEZING MODEL FOR WOODY PLANT CELLS |
本系統中英文摘要資訊取自各篇刊載內容。