Research on the mechanism of different nitrate accumulation in Chinese cabbage with different genotypes

Two Chinese cabbage ［Brassica campestris ssp. chinensis (L. ) Makino］ cultivars (SYM and HGQGC) different significant in nitrate accumulation were used in our research to investigate the mechanism involved in nitrate absorption. With 0.2 and 2 mmol/L NO-3 treatments, the nitrate concentration, nitrate uptake rate, nitrate reductase activity (NRA) and the expression level of NRT1 and 〖NRT2 were measured. The data suggested that firstly, the nitrate concentration in SYM was higher than that in HGQGC especially under higher nitrate treatment except for leaves with 0-2mmol/L NO-3 supply. The increment of nitrate concentration in SYM was also higher than that in HGQGC following the enhancement of nitrate in growing medium. Secondly, the nitrate uptake rate of SYM was higher than that of HGQGC with 0-20mmol/L NO-3 in growing medium, also especially with higher NO-3 solution. Thirdly, with 2mmol/L NO-3 treatment, the expression patterns of 〖NRT2 was consistent with the nitrate concentration in root, leaves and stem, that means the expression levels of 〖NRT2 in SYM was higher than that of HGQGC, while the same instance only occur in root for NRT1 expression. under 0.2 mmol/L NO-3 treatment, only in stem the nitrate concentration, expression level of NRT1 and 〖NRT2 were all higher in SYM than those in HGQGC. Fourthly, the different expression patterns of NRT1 and 〖NRT2 maybe partly responsible for the different nitrate accumulation between cultivars and there must be some unknown genes also participated in nitrate accumulation especially in 0.2 mmol/L NO-3 treatment. Lastly, the NRA of SYM was also higher than HGQGC that means the higher nitrate use efficiency in SYM.