中文摘要：

用水培法研究了Ce（Ⅲ）对紫外辐射（UV-B,280～320nm）胁迫下大豆幼苗光合原初反应的影响。结果表明,20mg·L-1CeCl3能有效减缓紫外辐射（T1/3.34kJ·m-2和T2/11.76kJ·m-2）胁迫所导致的叶绿素与类胡萝卜素含量减少、光能转换效率（Fv/Fm）及传递能力（Fv/F0）降低,且对低剂量胁迫的调控效果优于高剂量,即以上指标Ce＋T1〉T1,Ce＋T2〉T2,Ce＋T1〉Ce＋T2。从光合原初反应的能量分配看,Ce（Ⅲ）能促使大豆叶片吸收光能的总量增加,加快内囊体膜上光电的转换和电子的传递,降低UV-B辐射伤害而导致的过剩激发能积累,从而消除过剩激发能诱发的膜脂过氧化对光合器官的潜在威胁。

英文摘要：

Effect of cerium （Ⅲ） on photosynthetic primary reaction in soybean seedlings under uhraviolet-B radiation （ UV-B, 280-320 nm） stress was studied with hydroponics under laboratory conditions. UV-B radiation （T1/3.34 kJ. m-2, T2/11.76 kJ. m-2） caused the decrease in chlorophyll（ Chl ） and carotenoid（Car） content, optimal photochemical efficiency of PS 11 （ Fv/Fm ） and light transport capacity（Fv/Fo）, and the excess accumulation of excitation energy. The decrease degree of each index was positively related with UV-B radiation dosage. However, CeCl3（ 20 mg. L-1 ） increased Chl and Car content, Fv/Fm and Fv/Fo, compared with those of the controls. For Ce＋UV-B treatments, all of indices were still lower than those of the controls, but obviously higher than those of UV-B treatments. The sequence was followed as： Ce＋T1 〉 T1; Ce＋T2〉T2; Ce＋T1 〉Ce＋T2. The result indicated that Ce（ 20 mg-L-1） could alleviate UV-B-induced inhibition on photosynthetic prima- ry reaction, and that regulating effect of Ce on all indices mentioned above under low dosage of UV-B radiation was better than that under high dosage. As to the excitation energy distribution in photosynthetic light reactions in UV-B, Ce and Ce＋UV-B treatments, Ce（ Ⅲ ） could promote leaves absorbing more light energy by increasing Chl content, accelerate photoelectric conversion and electron transport in thylakoid membrane, and decrease the excess accumulation of excitation energy induced by UV-B radiation, which could alleviate the poten- tial damage on chloroplast structure due to aggravation of membrane lipid peroxidation.