| With the increase of population and the decrease of arable land, it has become an important issue to reduce the amount of nitrogen in the case of crop yield guaranteed in today’s agricultural development urgently needed research. In this research, the pot and hydroponics experiments were conducted. The purpose of this article was to ascertain the mechanism of nitrogen efficient utilization through analyzing characteristics of accumulation of dry matter production and nitrogen, translocation and nitrogen component in plant and morphological and physiological characteristics of root on the basis of Nitrogen-efficient barley screening test. It can provide a scientific basis for the genetic improvement and efficient nitrogen management in barley. The main results were as follows:(1) Barley genotype with high and low nitrogen utilization efficiency was obtained through hierarchical cluster analysis by using yield as evaluation indexes. Barley genotype with high nitrogen utilization efficiency (high NUE) contains 8 materials, including DH61, DH121+, DH38, while barley genotype with low nitrogen utilization efficiency (low NUE) contains 11 materials, including DH33, DH96, DH80. Grain yield, nitrogen utilization efficiency for grain and nitrogen harvest index of high NUE were 82.08%,61.48% and 50.49% higher than those of low NUE respectively under low nitrogen treatment.(2) Dry matter weight and nitrogen accumulation of high NUE were significantly higher than those of low NUE under low nitrogen conditions in each growth stage. Therefore, dry matter accumulation and nitrogen absorption significantly affect grain yield and nitrogen use efficiency in each growth stage. The peak of dry matter weight of high NUE appeared in jointing to heading stage, degree of influence on grain production was 47.94%, while the peak of nitrogen accumulation appeared before jointing stage, degree of influence on grain production was 54.67%. Dry matter weight and nitrogen accumulation seriously affected Nitrogen utilization efficiency for grain in heading to mature stage, and the degree were 29.53%,48.70% respectively. Followed by seeding to jointing stage, the degree were 29.04% and 15.80% respectively. Therefore, improving capability of the dry matter production and nitrogen accumulation before jointing synergistically to increase production and NUE of barley.(3) Total root length, root surface area and root volume of high NUE (DH61 and DH121+) were significantly higher than low NUE (DH80). With increased levels of nitrogen supply, total root length, root surface area and root volume of less than 0.16mm diameter class roots decreases,0.16 to 0.48mm diameter class showed a single peak curve, and greater than 0.48mm diameter class showed a linear increase in the trend. Total root absorption area, a redox active absorption area and oxidation ability and reducing capacity of high NUE were significantly higher than low NUE. NR, GS, GOGAT and GDH activity of high NUE were significantly higher than low NUE. It promote root carbohydrate synthesis and inorganic nitrogen to organic nitrogen assimilation, and contributed to transport nitrogen to the shoots, thus significantly increased its aboveground nitrogen accumulation. Stepwise regression analysis showed that root length, root surface area and root volume of high NUE have the greatest influence on nitrogen accumulation. Good root morphology and development increased 0.16 to 0.48mm diameter class roots to nitrogen contact area for the roots to absorb nitrogen provides the basic conditions.(4) Nitrogen accumulation of high NUE before flowering are 1.48 times,1.36 times and 1.37 times higher than those of low NUE under low nitrogen (125 mg·kg-1), normal nitrogen (250 mg·kg-1), high nitrogen (375 mg·kg-1), adequate nitrogen accumulation of high NUE before flowering lay the foundation material qualitative. High NUE have strong nitrogen transfer ability after flowering. DH61 and DH121+ transport rate was 75.27% and 83.25%, respectively, the amount of nitrogen transported to grain contribution rate of 76.37% and 81.72% respectively under low nitrogen supply. Higher transfer efficiency associated with different forms of nitrogen in plant composition and change. Under different nitrogen treatments, assimilable nitrogen content in stalk and leaf increased, functional nitrogen content changes smoothly and structural nitrogen content is reduced from flowering to filling, while assimilable nitrogen content increased, and structural nitrogen content slowly declined in grain. High NUE have a strong decline and nitrogen transport capacity of the structural nitrogen content. Functional nitrogen content decreased structural of high NUE in stem and leaf 49.65% and 62.54% under low nitrogen treatment from flowering to filling, and it decreased 66.54% and 28.17% from heading to maturity. Grain nitrogen content of high NUE in stems and leaves is decided by the structural nitrogen content decomposition and transformation after flowering,and structural nitrogen recycling in vegetative organs conducive to nitrogen use efficiency. |
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