Accumulation and distribution of nitrogen in triticale varieties with different nitrogen utilization efficiencies under different nitrogen application levels

Nitrogen (N) is a critical factor influencing yield and quality of triticale. To analyze the effects of N accumulation and distribution on N use efficiency (NUE) at different growth stages (tillering, jointing and heading) of triticale, a pot experiment with three N fertilization rates 0 (zero-N), 0.033 g(N)·kg^-1 (low-N) and 0.066 g(N)·kg^-1 (normal-N) and three triticale varieties two high NUE ('Clxt82', 'PI429186') and one low NUE ('Clxt74') was carried out. The distribution of N in plant organs, and contents of different N forms were analyzed at various growth stages. The results showed that high NUE triticale varieties were advantages in low N conditions. The differences in biomass between high and low NUE varieties gradually decreased with increasing N fertilization rates at heading stage. Above-ground biomass of 'Clxt82' was respectively 1.55 times, 1.19 times and 1.06 times that of 'Clxt74' under zero-N, low-N and normal-N treatments. Similarly, above-ground biomass of 'PI429186' was respectively 1.79 times, 1.35 times and 1.30 times that of 'Clxt74' under zero-N, low-N and normal-N treatments. N accumulation increased significantly with increasing N fertilization rates at different growth stages. Under low-N and normal-N treatments, N accumulation in both high NUE varieties was significantly higher than that in low NUE variety at tillering and jointing stages. However, no significant difference was noted between the varieties at heading stage. Allocation ratio of N in plant leaves and ears decreased with increasing N fertilization rates and the reverse was the case for plant stems. At tillering and jointing stages, N allocation ratios of stems of high NUE varieties were less than that of low NUE variety, and for leaves it was reverse. At heading stage, N allocation ratio of ears of high NUE varieties was higher than in low NUE varieties and the reverse was the case for leaves. Contents of different forms of N increased with increasing N fertilization rates at various growth stages. At jointing stage, assimilable N (AN) contents in 'Clxt82' and 'PI429186' leaves were respectively 1.31 times and 1.76 times that in 'Clxt74' under zero-N treatment, and 1.12 times and 1.35 times under low-N treatment. Then structural N (SN) contents were respectively 86.12% and 64.01%, and 80.82% and 71.51% that of 'Clxt74'. At heading stage, AN content in 'Clxt82' and 'PI429186' leaves were respectively 1.01 times and 1.11 times that of 'Clxt74' under zero-N treatment, and 1.04 times and 1.13 times under low-N treatment. Also SN content were respectively 74.99% and 63.08%, and 75.78% and 62.84% that of 'Clxt74'. However, functional N (FN) content was not significantly different for the varieties at various growth stages. High NUE varieties maintained N utilization and N cycle by reducing SN content and increasing AN content.