Studies On The Effect Of NRA On Nitrate Accumulation And Metabolism Regulation In Pakchoi

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.