中文摘要：

采用水培法研究了La对紫外辐射（UV—B，280—320nm）胁迫下大豆幼苗活性氧代谢的动态影响。实验结果表明，UV—B辐射（T1／15μW／cm^2和T2／45μW／cm^2）胁迫下，大豆幼苗质膜透性、丙二醛（MDA）、过氧化氢（H2O2）和脯氨酸含量先升（胁迫期）后降（恢复段），过氧化氢酶（CAT）活性先增（1—5d）后减（6-11d），T1组过氧化物酶（POD）活性在胁迫期逐渐升高，恢复期维持一较高水平后陡降，而T2组POD活性一直升高至第9d，尔后略有下降。La介入，使大豆质膜透性、MDA、H2O2与脯氨酸光致修复各时段变幅降低，La＋T1及La＋T2组CAT和POD酶活性显著高于各自的UV—B组（P〈0．05）。表明La对CAT、POD等抗氧化酶的调控作用，减轻了UV—B辐射对其功能的损伤，提高了清除活性氧的运行效率，降低了MDA浓度和脯氨酸含量，维持了质膜正常透性，且对低剂量（T1）的防护效果优于高剂量（T2），进而在防御系统层面实现了La对UV—B辐射伤害大豆幼苗的防护效应。

英文摘要：

The dynamic effect of lanthanum （ La3 ^＋ ） on reactive oxygen metabolism of soybean seedlings under elevated ultraviolet - B radiation （ UV - B ： 280 - 330nm） at 15 μW/cm^2 and 45 μW/cm^2 level was studied through hydroponics in laboratory. Our result showed that plasmolemma permeability, malonadialdehyde （MDA） content, the accumulation amount of hydrogen peroxide （ H2O2 ） and proline content of soybean seedlings gradually increased during UV - B stress period and subsequently decreased during recovery period. The dynamic tendency of catalase （CAT） activity of UV - B treatment was similar to that of plasmolemma permeability, MDA content, the accumulation amount of H2O2 and proline content. The activity of peroxidase （POD） firstly increased, kept on a high level and finally declined steeply when soybean seedlings were exposed to low level of UV - B radiation. However, POD activity rose all the time and declined slightly on the eleventh day when soybean seedlings were exposed under high level of UV - B radiation. With the add of La, as for plasmolemma permeability, MDA, the accumulation amount of H2O2 and proline content, their ranges of time intervals during photorepair were all declined and the activities of CAT and POD were significantly higher than those without La （ P 〈 0.05 ）. It suggested that the regulative effect of La on antioxidant enzymes such as CAT and POD could relieve the damage of UV - B radiation to these enzymes function, strengthen their capacities to scavenge reactive oxygen species （ROS）, improve the metabolism of ROS, decrease the concentration of MDA and the content of proline and maintain normal plasmolemma permeability. Further, the protection potential of La was better under low UV - B radiation than under high UV - B radiation. Thus, the protective effect of La on soybean seedlings under UV - B stress was carried out at the level of defense.