Abstract: 【Objective】 This study aimed to explore the characteristic of nitrogen metabolic in diallel cross generation of different maize genotypes after silking.【Method】Selection high nitrogen use efficiency hybrid maize plays an important role in high yield and high efficiency production of maize A full diallel cross was made with three stay-green inbred lines (Q319, CZ01, VA91) and three non-stay-green inbred lines (BM, B73, MO17) in field. The physiological traits of nitrogen metabolic in diallel cross generation were analyzed.【Result】Content of nitrogen in leaf graphed as inverted “V”-shapes after silking stage in different maize genotypes. The peak of nitrogen content in leaf occurred in filling stage. Content of nitrogen in stem-sheaf and sheath reduced with the extension of the growth duration. Content of nitrogen in leaf, stem-sheaf and sheath of stay-green (SG) inbred lines were much higher than those in non-green-stay (NSG) ones. Nitrogen accumulation before silking stage (NABS), nitrogen accumulation after silking stage (NAAS) and total nitrogen accumulation (TNA) in SG self cross were 20.00%, 82.30% and 45.23%, respectively, higher than those in NSG ones. However nitrogen translocation, nitrogen translocation rate and nitrogen harvest index in SG were 51.28%, 66.59% and 14.32% , which was significantly lower than those in NSG ones. TNA of SG was about 50% and TNA of NSG was only 40% after silking stage. Crude protein content in leaf and stem-sheaf of SG were 108.23% and 33.63%, higher than those in NSG ones. The straws were still higher valuable after harvesting. Some key enzymes to nitrogen metabolic activity such as nitrate reductase (NR) activity, glutamate synthetase (GOGAT) and glutamine synthetase (GS) in leaf of stay-green type were significantly higher than those in non-green-stay types. NR activity in leaf increased firstly and the peak occurred in filling stage after silking stage in different maize genotypes. GS activity, GOGAT activity and soluble protein content in leaf increased firstly, and the peak occurred 15 days after silking. Correlation analysis between stay-green degree, content of nitrogen, soluble protein content, GS activity, GOGAT activity and NR activity indicated that there existed significantly or highly significant positive correlations. Activities of those key enzymes on nitrogen metabolism were significantly important for nitrogen assimilation. 【Conclusion】 High nitrogen metabolism level is one of the nutrition physiological basis which makes leaves keep green for long time. Compared with the non-stay-green types, stay-green genotypes behave higher activities of key enzymes to nitrogen metabolic and higher nitrogen asorption and assimilation at late growth stage. In conclusion, character of stay-green could be used as an important agronomic trait in selecting high nitrogen efficient genotypes and inbred line.

Key words: maize (Zea mays L.) , genotype , stay-green trait , nitrogen metabolism