中文摘要：

以低硝酸盐积累基因型（东妃）和高硝酸盐积累基因型（高雄甜脆）两种小白菜为材料,采用溶液培养法研究了增施CO2降低蔬菜硝酸盐积累的生理机制。结果表明,CO2浓度升高能显著提高2种基因型小白菜的生物量和硝酸还原酶活性,并降低根、茎叶各部位的硝酸盐含量。CO2浓度升高不仅促进了植株对硝态氮的吸收,而且植株吸收硝酸盐的累积量增幅均高于鲜重的增幅。由此可见,除了鲜重增加的稀释作用,处理后生理机制的变化也可能是CO2浓度升高引起硝酸盐含量降低的重要原因。研究还表明,增施CO2后＂东妃＂的硝酸盐含量降低百分率与硝酸还原酶活性的增加百分率呈极显著相关,而＂高雄甜脆＂的硝酸盐含量降低百分率则与鲜重的增加百分率的相关性达极显著水平。说明增施CO2后植株各部位硝酸还原酶活性提高及鲜重的增加均为引起硝酸盐含量降低的重要原因,但贡献率具有明显的基因型差异。

英文摘要：

Hydroponic experiments were carried out to study the mechanisms of CO2 enrichment-induced decrease of nitrate accumulation in two genotypes of Chinese cabbage（low nitrate accumulation genotype Dongfei and high nitrate accumulation genotype Gaoxiongtiancui）.Results showed that elevated CO2 not only significantly increased the biomass and nitrate reductase（NR） activity,but also significantly decreased the nitrate concentration in leaves,stems and roots of both genotypes.In addition,nitrate uptake by plants was also enhanced by elevated CO2,and the elevated CO2-increased percentage of nitrate uptake was higher than that of biomass,indicating that not only the dilution effect resulted by biomass increase,but also the change of physiological processes are the reasons leading to the decrease of nitrate accumulation in plants under elevated CO2.Moreover,the decreased percentage of nitrate concentration was correlated well with the increased percentage of NR activities in Dongfei genotype,while in Gaoxiongtiancui genotype the decreased percentage of nitrate concentration was greatly correlative to the increased percentage of biomass.These results demonstrate that the increases of both NR activity and biomass are the pivotally mechanisms reducing nitrate accumulation in vegetable under CO2 enrichment,whereas distinct genotypic differences exist in the contribution rates of these two mechanisms.