Difference In N Efficiency Among Maize Inbred Lines And Response Of Maize To N Supply

The genotypic different in responses of maize inbred lines (Zi330 and Chen94-11) to nitrate levels was studied by using maize inbred lines differing in N efficiency which was selected from field and pot experiments, the main results were summarized as follows: 1. Under N application levels, Zi330 and Chen94-11 were grown in Dongbeiwang to study the genotypic difference of accumulation and uptake of nitrogen. The results showed that the biomass of shoot have no significant difference in two maize seedlings, but significant genotypic difference existed among Zi330 and Chen94-11 after transplanting 60 days. During transplanting 60 days, two maize inbred lines cause an increase in the biomass, but the dry weight of every organ for Zi330 was higher than for Chen94-11. Maximum absorbing rate of N was from stem elongation to earing stage, but Zi330 was significantly higher on the biomass and accumulation of N than Chen 94-11. The nitrogen accumulated on vegetative organs was transferred into grain gradually by senescence of plant. The model of accumulation and redistribution of nitrogen in different organs was dependence on types of cultivars. 2. Zi330 and Chen94-11 which were significantly different in N efficiency were grown in solutions supplied with different nitrogen to study the differences in N uptake and utilization by maize plants. The results showed that dry weight of shoot, N content decreased for both Zi330 and Chen94-11 as the N supplying decreased, but dry weight of root and root/shoot ratio increased. Zi330 with a higher N efficiency than Chen94-11 had a great tolerance to low N stress. The dry weights of both shoot and root for Zi330 were higher than for Chen94-11 when they were in low N condition. The variation of N use efficiency for the two maize inbred lines was due to the difference in root biomass, rather than N concentration in root. 3. Zi330 was used to investigate the aerenchyma formation of Primary seminal root under conditions of different nitrogen levels and phosphorus levels. The results indicated that aerenchyma formation took place earlier in N stressed maize root than plant biomass difference occurred high N and low N treatment, it was also earlier than the point of root/shoot ratio, specific N content of shoot and root. A positive correlation existed between aerenchyma formation and low N stress. 4. Under quartz culture condition, Zi330 was supplied with different N forms (nitrate nitrogen, ammonium nitrogen, ammonium nitrate) to study the effect of N flows via phloem and xylem. The results showed that maize supplied with nitrate nitrogen cause an increase in dry matter and N content of shoot, N content in the xylem. N accumulation of upper leaves of maize supplied with NO3--N,NH4+-N and NH4NO3-N account for 80%, 79% and 92% with whole plants. Ammonium nitrogen and ammonium nitrate inhibited the growth of plants and uptake of N, K+ and Ca2+.