Major antioxidants were studied in three Citrus (C. reticulata, C. sinensis, and C. paradisi) under low-temperature stress (1, −1, −3°C). Regulatory effects of exogenous proline (0, 15, 20 mM) were studied as well. The results indicated that treatment of exogenous proline reduced both hydrogen peroxide and lipid peroxidation in three Citrus species. The high-performance liquid chromatography chromatograms at −3°C showed that exogenous proline increases chlorogenic, gallic, p-coumaric, and ferulic acid from phenolic acids as well as naringin, quercetin, and rutin from flavonoids. The amount of oxalic, citric, and ascorbic acid increased with increasing proline concentration but tartaric acid decreased. Exogenous proline increased Gamma-aminobutyric acid although its content showed no significant difference between 15 and 20 mM. Both low-temperature stress and treatment of proline induced the activity of ascorbate peroxidase (APX) and catalase. In contrast, lipoxygenase activity reduced with temperature decrease as well as increasing exogenous proline levels. Also, treatments of low temperature and proline showed that the levels of endogenous proline, catalase and APX in C. reticulata are higher compared with two other species and their amount increases with the reduction of temperature.

在低温胁迫（1，-1，-3°C）下，对三种柑橘（C. reticulata，C。sinensis和C. paradisi）中的主要抗氧化剂进行了研究。还研究了外源脯氨酸（0、15、20 mM）的调节作用。结果表明，外源脯氨酸的处理减少了三种柑橘属植物的过氧化氢和脂质过氧化作用。−3°C时的高效液相色谱图表明，外源脯氨酸增加了绿原，没食子，p-香豆酸和阿魏酸（来自酚酸）以及柚皮苷，槲皮素和芦丁（来自类黄酮）。草酸，柠檬酸和抗坏血酸的含量随脯氨酸浓度的增加而增加，但酒石酸的含量则减少。外源脯氨酸增加了γ-氨基丁酸，尽管其含量在15和20 mM之间没有显着差异。低温胁迫和脯氨酸处理均诱导抗坏血酸过氧化物酶（APX）和过氧化氢酶的活性。相反，脂氧化酶活性随温度降低以及外源脯氨酸水平升高而降低。此外，低温和脯氨酸的处理显示网纹衣藻中内源性脯氨酸，过氧化氢酶和APX的水平 与其他两个物种相比，它们的含量更高，并且它们的数量随着温度的降低而增加。