【作者】 梁亮；

【导师】 袁希汉；

【作者基本信息】 南京农业大学 ， 蔬菜学， 2008， 硕士

【摘要】 目前,蔬菜中硝酸盐的积累引起了许多国家的重视,环境卫生学大量试验证明,硝酸盐可以通过细菌的作用在动物体内外还原成亚硝酸盐,亚硝酸盐不仅会使人体中毒缺氧导致高铁血红蛋白症,还会导致人体消化系统的癌变等。由于人体摄取的硝酸盐有81.2%来源于蔬菜,小白菜（Brassica campestris L.ssp Chinesis Makino）是极易富集硝酸盐的蔬菜,又是南方地区占蔬菜上市量达33%的大众化蔬菜,因此研究硝酸盐在小白菜中的积累具有重要意义。影响硝酸盐积累的内外因素很多,其中,硝酸还原酶活性（nitrate reductase activitM NRA）是硝酸盐还原的主要限速因子。小白菜品种间的硝酸盐含量和硝酸还原酶活性差异显著,本研究主要采用“上海青、苏州青、兴化青梗菜、引02、青丰一号、兔子腿矮脚黄”的高代自交系为试验材料,利用水溶液培养法,围绕NRA对小白菜硝酸盐积累及生理机制影响进行了研究,结果表明:1.氮素形态对小白菜体内硝酸盐积累和NRA的影响在全硝态氮供应的N1处理组的硝酸盐含量显著高于硝/铵等比处理的N2组和全铵态氮处理的N3组;N1组的NRA略高于N2组,并无显著性差异,但N1组和N2组的NRA均极显著高于N3组,全铵态氮的N3处理组硝酸盐含量和NRA都最低。N2处理组的品质和产量最高,N1略低于N2处理组,而N3的品质和产量最低。在全硝态氮供应下,根系对NO₃^-的吸收速率最高,而随着铵态氮比例的增加,其吸收速率随之降低。2.根部NRA对小白菜硝酸盐和可溶性糖代谢的影响根系NRA受抑的情况下根系对NO₃^-吸收速率显著下降,而地上部的硝酸盐含量并无显著差异。同时,根系NRA受抑条件下,其根系可溶性糖浓度增加,而地上部可溶性糖浓度则相对减少。3.小白菜光合性能与NRA关系1)光照强度是制约NRA和硝酸盐含量的主要因素,尤其对NRA的高低影响极显著。2)NRA的降低会对光合速率产生一定的反作用。而叶绿素含量、气孔导度、胞间CO₂浓度和蒸腾速率在NRA抑制前后无显著变化,不受NRA的直接影响。3)在一定的硝态氮浓度范围内(=8mmol·L¹),NRA的升高对净光合速率的升高有促进作用。以上结论表明,光合性能与NRA存在着一定的相互促进和相互制约的关系。4.钼锰不同施用方式对小白菜NRA和硝酸盐含量的影响钼显著提高了小白菜的NRA,使NO₃^-显著降低,锰的施用,对NRA的影响不明显,但可以使硝酸盐含量降低,钼和锰的施用均可提高可溶性糖含量和Vc含量,与钼相比,锰对可溶性糖含量和Vc含量的提高更为显著。钼锰配施对提高NRA和降低硝酸盐含量最为明显,同时配施时对可溶性糖含量和Vc含量的提高也最为明显。叶面喷施与营养液根部结合施用对各生理指标的影响效果要明显高于叶面施用而略高于营养液施用。更多还原

【Abstract】 Concentrations of nitrate in vegetables have been the focus of attention in several countries. A lot of reaserch on environment hygienics show that nitrate may reduce to nitrite which can lead to some diease such as cancer in animals. The nitrate absorbed by human is 81.2% derived from vegetable. Furthermore, nitrate was very easy accumulated in pakchoi which is a very popular vegetable which occupied 33% of the whole vegetable market in China, and NRA （Nitrate Reductase Activity） was a main limit factor in nitrate reduced.In this study soluble culture was used for physiological mechanism of nitrate accumulation and NRA in pakchoi. There was significant difference of nitrate content and NRA between different genotypes of vegetable crops. Six genotypes were used in this study: Shanghaiqing, Suzhouqing, Xinghua qinggengcai, Yin02,QingfengNo.l,Tuzitui aijiaohuang. The results went as followed:1 Effects of nitrogen forms on nitrate content and nitrate reductase of pak-choiThe content of nitrate in the N1 system which was offered pure NO₃^- is obviously higher than the system of N2 （NO₃^-/NH₄⁺=1/1） and N3（NO₃^-/NH₄⁺=0/1）.NRA in N1 has a little higher than N2, but NRA in N1 and N2 is much obviously higher than N3.The nitrate content and NRA is the lowest in N3 which is treat with pure ammonium. Qualities and yield of N2 are the highest, N1 is a little lower than N2, N3 is the lowest neither in qualities or yield. The absorb rate of NO₃^- in root is the fastest when pure nitrate was offered, but the absorb rate was decreasing with the ammonium increasing.2 Effect of NRA in root on the absorb and metabolism in nitrate of pakchoiThe absorb rate of NO₃^- reduced by inhibiting NRA in root, but there is no significant dramatically difference of the nitrate content. Furthermore, if we inhibit NRA in root,the concentration of soluble sugar increased and the concentration reduced in shoot. 3 Studies on the relationship of NRA and photosynthetic characters of pakchoiThe main characters of NRA and nitrate content controlling factor are light intensity especially on NRA. In addition, NRA reduced can feed back the photosynthetic, but chlorophyll content, Cond and Ci did not change obviously after NRA reduced. What’s more, the grown of NRA can promote the photosynthetic when the nitrate content is lower than 8mmol·L^-1.To sum up,the conclusion shows that photosynthetic characters and NRA have some relationship both in promotion and restriction.4 Effects of Molybdenum and Manganese on NRA and nitrate contentMo was significantly improved NRA and reduced nitrate in two genotype of pakchoi. However, Mn could not improve NRA significantly, but it can also reduce nitrate content. Both of Mo and Mn could improve the content of soluble sugar and Vc but Mn improved them more significantly compare with Mo. Mo cooperated with Mn had improved NRA and reduced nitrate content the most significant, in addition, it also improved the content of soluble sugar and Vc the most significant. It is the most effective if Mo and Mn fertilized both in leaves and root, and fertilized in root is better than in leaves.更多还原