中文摘要：

以硝酸盐低积累和高积累2个品种小白菜（Brassica campestris L.ssp.）为试验材料,采用盆栽的方式研究不同浓度镉（Cd）处理对小白菜叶片中硝酸盐、铵态氮、游离氨基酸、可溶性蛋白、氮代谢相关酶活性及光合作用的影响。结果表明,在试验设置的镉含量（0-7.0mg/kg）范围内,随着镉含量的升高,硝酸盐低积累品种小白菜的生长受到显著抑制;低积累品种叶片的硝酸盐和可溶性蛋白含量均呈先增加后降低的趋势,高积累品种则逐渐降低。镉胁迫促进铵态氮和游离氨基酸在小白菜叶片中的累积,其中,低积累品种表现得更为明显。镉胁迫下,2个品种小白菜的硝酸还原酶活性均受到显著抑制。随着镉含量的升高,与对照相比,2个品种小白菜的净光合速率、气孔导度、胞间CO2浓度和蒸腾速率均呈先增加后降低的趋势。镉胁迫使得小白菜对氮素的吸收代谢紊乱,光合速率降低,且胁迫的响应程度与小白菜的基因型有关,在硝酸盐低积累品种中表现得更为显著。

英文摘要：

A pot experiment was conducted to investigate effects of cadmium stress on nitrogen me- tabolism and photosynthesis of low nitrate accumulator and high accumulator of Chinese cabbages （Brassica campestris L. ssp. ） Cd was applied with five levels of 0,0. 5,1.0,5.0 and 7. 0 mg/kg soil. The fresh weight, concentrations of nitrogen, ammonium, free amino acid, and soluble protein, activities of nitrate reductase （NR）,glutamine synthetase （GS） of leaves, net photosynthetic rate （Pn）, stomatal con- ductance （Gs）,intercellular CO2 （Ci） and transpiration rate （Tr） were determined. The results showed that the fresh weight of the low nitrate accumulator decreased significantly with the increase of Cd con- centration. The concentrations of nitrogen and soluble protein in the leaves of the low nitrate accumula- tor decreased with the increase of Cd concentration. Accumulations of ammonium and free amino acid in the leaves of both Chinese cabbage cultivars were detected under the Cd stress, especially in the low nitrate accumulator. Cadmium induced a significant inhibition on the activities of nitrate reductase（NR） in both cultivars. Under the Cd stress,activities of nitrate reductase （NR） and glutamine synthetase （GS） in leaves of the low accumulator were lower than those in leaves of the high accumulator. Treated with both 0. 5 mg/kg and 1.0 mg/kg, net photosynthetic rate （Pn）, stomatal conductance （Gs）, intercellular CO2 （Ci） and transpiration rate （Tr） of both Chinese cabbage cultivars increased. Treated with high Cd concentrations （5.0 mg/kg and 7.0 mg/kg） these parameters were decreased. It is indicated that cadmi- um disturbed nitrogen metablism and decreased net photosynthetic rates of both Chinese cabbage culti- vars. All indexes of changes for the low nitrate accumulator were greater than that for the high nitrate accumulator.