Mechanism of nitrate accumulation of Chinese cabbage under properly enhanced ammonium

In order to study the underlying mechanisms of properly enhancing ammonium to reduce nitrate content in(Chinese) cabbages and the nitrate accumulation capacity of different cultivars and different organs of Chinese cabbage,(nitrate) contents in leaf blades,petioles and roots,the amonut of nitrate and ammonium adsorptive capacity and nitrate(reductase) activity of these three organs of the two cultivars of Chinese cabbage(Shanghaiqing,SHQ and Liangbaiye 1,LB1),incubated using two nutrient solution with NO~-_3-N/NH~+_4-N being 100∶0 and 75∶25 respectively,were assayed.The results obtained indicated that properly enhancing ammonium reduced nitrate content in leaf blades,petioles and roots by 22%,15% and 22% respectively,but adsorptive capacity of nitrate was reduced by 7.5%.The nitrate contents in different organs were: petioles leaf blades roots.Nitrate reductase activity(NRA) in leaf blades was 27 and 9 times higher than that in petioles and roots,respectively.Leaf blade was the main organ responsible for the reduction of nitrate.(Nitrate) contents in leaf blades,petioles and roots of Liangbaiye 1 were higher than those in the organs of Shanghaiqing by 3%,38% and 34%,respectively.The amount of nitrate taken up by Liangbaiye 1 was only 11% more than that taken up by Shanghaiqing,but the nitrate reducatse activity of leaf blades,petioles and roots was 44%,56% and 38% lower than those of Shanghaiqing.The falling of accumulation of nitrate in plants was mainly attributed to the proper enhancing ammonium reduced the adsorptive capacity of nitrate.Different functions and different construction of organs resulted in their different nitrate accumulation capacity.The variance of nitrate accumulation of different cultivars laid on the variance of the ability in the reduction of nitrate.