Xishuangbanna Tropical Botanical Garden, The Chinese Academy of Sciences, Mengla, Yunnan, China.
Protoplasma. 2010 Mar;239(1-4):57-67. doi: 10.1007/s00709-009-0083-2. Epub 2009 Nov 11.
Cytological and physiological changes during cryopreservation were studied in maize embryos at 35 days after pollination (DAP). Both dehydration and freezing caused cytological damage, such as plasmolysis, swelled mitochondria, increased heterochromatin, and nuclear shrinkage. Dehydration alone slightly impaired plasma membrane integrity while a drastic increase in electrolyte leakage was observed after freezing of embryos with moisture content above 23%. Damage to cellular ultrastructure and plasmalemma integrity was negatively related to moisture content in unfrozen embryos and positively related in frozen embryos. The pattern of changes in activity of antioxidant enzymes differed from one another during dehydration and/or freezing-thawing treatment. Dehydration increased activity of ascorbate peroxidase (APX) and glutathione reductase (GR) but decreased activity of superoxide dismutase (SOD) and dehydroascorbate reductase (DHAR). Freezing further decreased GR and SOD activity and resulted in extremely low DHAR activity. Embryos at intermediate moisture contents had low catalase (CAT) activity before freezing but highest CAT activity after freeze-thaw. Both dehydration and freezing promoted membrane lipid peroxidation which resulted in an approximately threefold increase at most in the malondialdehyde content in postthaw embryos. Changes in viability of postthaw embryos can be closely related to damage in cellular ultrastructure and plasmalemma integrity but directly related neither to antioxidants nor lipid peroxidation levels.
对授粉后 35 天（DAP）的玉米胚胎进行了冷冻保存过程中的细胞学和生理学变化研究。脱水和冷冻都会导致细胞损伤，如质壁分离、线粒体肿胀、异染色质增加和核收缩。单独脱水轻微损害质膜完整性，而在水分含量高于 23%的胚胎冷冻后，观察到电解质泄漏急剧增加。细胞超微结构和质膜完整性的损伤与未冷冻胚胎中的水分含量呈负相关，而与冷冻胚胎中的水分含量呈正相关。抗氧化酶活性在脱水和/或冻融处理过程中的变化模式彼此不同。脱水增加了抗坏血酸过氧化物酶（APX）和谷胱甘肽还原酶（GR）的活性，但降低了超氧化物歧化酶（SOD）和脱氢抗坏血酸还原酶（DHAR）的活性。冷冻进一步降低了 GR 和 SOD 的活性，并导致 DHAR 活性极低。在冷冻之前，中间水分含量的胚胎 CAT 活性较低，但在冻融后 CAT 活性最高。脱水和冷冻都会促进膜脂过氧化，导致解冻后丙二醛含量增加约三倍。解冻后胚胎活力的变化与细胞超微结构和质膜完整性的损伤密切相关，但与抗氧化剂或脂质过氧化水平没有直接关系。
