Growth traits and nitrogen assimilation-associated physiological parameters of wheat (Triticum aestivum L.) under low and high N conditions

摘要

In this study, 14 wheat cultivars with contrasting yield and N use efifciency (NUE) were used to investigate the agronomic and NUE-related traits, and the N assimilation-associated enzyme activities under low and high N conditions. Under deifcient-N, the cultivars with high N uptake efifciency (UpE) and high N utilization efifciency (UtE) exhibited higher plant biomass, yields, and N contents than those with medium and low NUEs. The high UpE cultivars accumulated more N than other NUE type cultivars. Under sufifcient-N, the tested cultivars showed similar patterns in biomass, yield, and N content to those under deifcient-N, but the varietal variations in above traits were smal er. In addition, the high UpE cultivars displayed much more of root biomass and larger of root length, surface area, and volume than other NUE type cultivars, indicating that the root morphological traits under N deprivation are closely associated with the plant biomass through its improvement of the N acquisition. The high UtE cultivars showed higher activities of nitrate reductase (NR), nitrite reductase (NIR), and gluta-mine synthetase (GS) at stages of seediling, heading and ifl ing than other NUE type cultivars under both low and high N conditions. Moreover, the high UpE and UtE cultivars also displayed higher photosynthetic rate under deifcient-N than the medium and low NUE cultivars. Together, our results indicated that the tested wheat cultivars possess dramatical y genetic variations in biomass, yield, and NUE. The root morphological traits and the N assimilation enzymatic acitivities play critical roles in regulating N accumulation and internal N translocation under the N-starvation stress, respectively. They can be used as morphological and biochemical references for evaluation of UpE and UtE in wheat.