膜脂过氧化作为扁桃品种抗寒性鉴定指标研究

研究不同低温胁迫下（３℃，一２℃和一ｌ０℃下分别处理０．５、３、６、９、ｌ２ｈ）扁桃离体叶片中ＭＤＡ含量、ＣＡＴ活性和类胡罗Ｌ素含量以及反映组织受伤害程度的膜透性变化和叶绿素降解间的关系，以探明膜脂过氧化在扁桃叶片低温伤害中的作用。３℃处理初期，ＣＡＴ活性、类胡罗卜素含量显著增加，叶片无明显伤害症状（水渍、黄化等）；一２Ｃ和一ｌ０℃下随处理时间的延长，叶片膜透性增大、叶绿素含量下降、ＭＤＡ积累增多；同时ＣＡＴ活性、类胡罗Ｌ素含量显著下降。ＭＤＡ含量的增加与组织受伤害程度（膜透性增加及叶绿素降解）及抗氧化系统（ＣＡＴ和类胡罗Ｌ素）水平下降之间具有极显著的相关性。以７个扁桃品种的田间越冬伤害指数及冬季所测枝条的ＬＴ５０代表植株的冬季抗寒性，以一５℃下处理４ｈ和８ｈ后所测叶片ＭＤＡ相对含量代表叶片的抗寒性，发现２者呈显著的相关性，表明ＭＤＡ可以作为鉴定扁桃品种抗寒性的指标。

Evaluation of Lipid Peroxidation for Use in Selection of Cold Hardiness Cultivars of Almond

Effects of low temperature stress on lipid peroxidation, membrane and chlorophyll stability, and catalase (CAT) activity and carotenoid content were evaluated under laboratory freezing tests (3℃, -2℃ and -10℃ for 0.5, 3, 6, 9, and 12h, respectively), for possible use as cold hardiness selection criteria, in detached leaves of two almond cultivars (‘NePlus' and ‘Nonpareil', differing in cold tolerance). The application of moderate chilling treatment (3℃ within 9h) to almond leaves had significantly elevated levels of CAT activity (‘Nonpareil' +17%～94%, ‘NePlus' +38%～107%) and carotenoid content (‘Nonpareil' +6%～31%, ‘NePlus'+10%～32%). Severe freezing treatments (-2℃ and -10℃) caused considerable injury in almond leaves as indicated by reduction in chlorophyll content (‘Nonpareil' -26%, -44% and ‘NePlus' -42%, -67%, respectively) and increasing in electrolyte leakage (‘Nonpareil' +76%, +275% and ‘NePlus' +196%,+379%, respectively ) , and enhanced oxidative stress as indicated by increasing in malondiadehyde (MDA) content ( ‘Nonpareil'+43%,+81% and ‘NePlus' +70%, +110%, respectively), and decreasing in levels of antioxidants (CAT activity and carotinoid content). The decrease in antioxidant system and the increase in oxidative damage are closely correlated. These results provide some evidence for the view that low-temperature responses in plants is due, at least in part, to oxidative stress, as a source of injury and as a signal to increase antioxidant defenses. We also found that the cold resistance of plant (measured by winter injury index of field plants and LT50 of current year shoots in winter) correlated to that of leaves (measured by MDA content in leaves under laboratory freezing test, -5℃ for 4h and 8h) in 7 almond cultivars.