镉对黄瓜幼苗光合作用、抗氧化酶和氮代谢的影响

采用营养液培养的方法，研究了不同浓度镉（Cd）处理对黄瓜幼苗植株生长、光合作用、抗氧化酶以及氮代谢相关酶活性的影响。结果表明，随着Cd处理浓度的增加，黄瓜植株生长受到明显抑制，叶绿素a、b、类萝卜素含量显著降低；Cd处理使净光合速率（Pn）和气孔导度（Gs）下降，而细胞间CO2（Ci）升高。高浓度Cd处理显著降低了黄瓜的原初光能转换效率(Fv/Fm)。10和100 mol/L的Cd处理使抗氧化酶过氧化氢酶（CAT、）愈创木酚过氧化物酶（POD）、超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APX）活性均有不同程度的提高，而当Cd浓度达到200 mol/L，抗氧化酶的活性均受到显著抑制。随着Cd处理浓度的增加，硝酸还原酶（NR）、谷氨酰氨合成酶（GS）、谷氨酸合成酶（GOGAT）活性均受到明显抑制。

Effects of cadmium on photosynthesis, antioxidant enzyme and nitrogen metabolism of cucumber seedlings

A solution culture experiment was conducted to study the effects of Cd on plant growth, photosynthesis, an-tioxidant enzyme activity and nitrogen metabolism of cucumber seedlings. The results indicate that cucumber seedling growth, chlorophyll (a and b) and carotenoid contents, net photosynthetic rate (Pn), and stomatal conductunce(Gs) are decreased with the increase of Cd concentration, while intercellular CO2 (Ci) are significantly increased. The primary maximum photochemical efficiency of PSII (Fv/Fm) is significantly decreased by high concentrations of Cd. Under the Cd 10 and 100 μmol/L treatments, activities of catalas (CAT), guaiacol peroxidase (G-POD), superoxide dismutase (SOD) and ascorbate peroxidase (APX), are increased, while under the Cd 200 μmol/L treatment, their activities are dramatically inhibited. With the increase concentration of Cd, the activities of nitrate reductase (NR), glutanine syn-thetase (GS) and glutamate synthase (GOGAT) are significantly decreased.