Physiological mechanisms for the difference of nitrate accumulation in two cultivars of non-heading Chinese cabbage | 2个不结球白菜品种硝酸盐累积差异的生理机制

中国人. 摘　　要：采用0.5、2.0、5.0 mmol.L-1NO3-3个浓度和3.75 mmol.L-1NO3-与1.25 mmol.L-1NH4＋混合浓度,对2个不结球白菜品种上海青（低硝酸盐累积品种）和亮白叶1号（高硝酸盐累积品种）进行水培试验,研究了供氮水平对硝酸还原酶活性（NRA）、硝酸盐含量和光合速率的影响。结果表明：不结球白菜硝酸盐含量存在品种和器官差异（P〈0.05）。亮白叶1号硝酸盐含量高于上海青,不同器官硝酸盐含量从高到低依次是：叶柄、叶片、根系,硝酸盐含量随外界供NO3-浓度的增加而增加,部分供NH4＋降低了硝酸盐含量;上海青NRA高于亮白叶1号（P〈0.05）,不同器官NRA从高到低依次是：叶片、根系、叶柄,叶片和根系的NRA随外界NO3-浓度的增加而升高,部分供NH4＋降低了不结球白菜NRA;在全NO3-处理下上海青叶片光合速率显著高于亮白叶1号（P〈0.05）,提高NO3-浓度可在一定程度上促进光合速率,部分供NH4＋使光合速率有所降低。总之,上海青比亮白叶1号具有更高的NRA和光合速率,使其具有更强的NO3-还原同化能力,从而减少了NO3-在体内的积累。

英语. Two cultivars of non-heading Chinese cabbage（Shanghaiqing,cultivar of lower nitrate content;Liangbaiye 1,cultivar of higher nitrate content）were hydroponically grown in four different nutrient solutions containing 0.5,2.0,5.0 mmol・L-1 NO3 and 3.75 mmol・L-1 NO3-mixing with 1.25 mmol・L-1 NH4＋,respectively.Effects of N supplement on nitrate reductase activity（NRA）,NO3-content and photosynthetic rate were studied.The results were listed as follows：NO3-content in Liangbaiye 1 was higher than that in Shanghaiqing and also showed significant differences between their organs（P0.05）.NO3-contents in organs were in the decreasing order of petiole,leaf blade and root.NO3-content increased with the increasing of NO3-concentrations outside.Proper enhancing NH4＋ reduced NO3-content.Shanghaiqing got higher NRA than that of Liangbaiye 1 under all treatments（P0.05）.NRA in different organs was in the decreasing order of leaf blade,root and petiole.NRA of leaf blade and root increased with the increasing of NO3-concentrations outside,while reduced when NO3-was partially replaced by NH4＋.Under the treatment of NO3-,photosynthetic rate in leaf blades of Shanghaiqing was significantly higher than that of Liangbaiye 1（P0.05）.Increase of NO3-concentrations outside promoted photosynthetic rate of leaf blades,while some supply of NH4＋ reduced it.In general,Shanghaiqing had the higher NRA and photosynthetic rate compared with Liangbaiye 1,which was helpful for the reduction and assimilation of NO3