| A field experiment was conducted in the super-high-yield experiment plot in 16th proving ground of Shandong Denghai seed industry Co., LTD and State Key Laboratory of Crop Biology, Shandong Agricultural University in 2009-2010. DengHai661(DH661), JingHai5 (JH5), ZhengJie2(ZJ2) and XunDan20(XD20) were selected as test varieties, under four nitrogen treatments of 0, 207, 310.5 and 414kg N·hm-2. In 2010, stay-green maize variety DH661, and ZJ2 was selected as test materials, and four nitrogen treatments of 0, 207, 310.5 and 414 kg N·hm-2 were confirmed., the physiological basis of leaves stay-green characteristics and the impact of nitrogen regulation to various stay-green hybrids were evaluated using various stay-green hybrids as materials in super-high yield conditions. The main conclusions were as follows.1 Yield and quality characteristic of super-high-yield summer maize and nitrogen regulation1.1 Yield and quality characteristic of super-high-yield summer maizeUnder the same nitrogen application amount(0-621kg N·hm-2), the yield of stay-green maize was higher than that of non-stay-green maize. The average yields of DH661 and ZJ2 were 12296.33, 10899.72 kg·hm-2, respectively, and the former was 1.13 times of the latter. The increase of rows ear played, the results of the increasing of ear length and kernels row a significantly contribution to yield.The average contents of essential amino-acid, non-essential amino acid, crude fat and free amino-acid of high-yield stay-green variety were higher than that of the non-stay-green variety. There was no variance in average contents of starch and soluble sugar in the two varieties.1.2 Nitrogen regulation on yield and quality of different super-high-yield summer maizeThe effect of nitrogen regulation to yield differed with different stay-green maize varieties. Both the yield of stay-green maize DH661 and non-stay-green ZJ2 reached their maximum value under 414 kg N·hm-2 condition(13548.91, 11902.45 kg·hm-2, respectively). From the fitting formulae, we can calculated the yield of DH661 and ZJ2 will reach 13727, 12317 kg·hm-2 when the nitrogen application amount were 443, 427 kg N·hm-2.The protein content of stay-green maize increased with the nitrogen amount. Under the treatment of applying 414 kg N·hm-2, non-stay-green maize reached the highest protein content. As the increase of nitrogen, crude fat content of stay-green maize improved gradually. However, pattern of non-stay-green maize was the opposite. Essential amino acid, non-essential amino acid and free amino acid of the base stay-green maize and non-stay-green maize increased as the nitrogen application increased. Along with increase of nitrogen, amino acid content also increased. The content of starch and soluble sugar showed a trend first increase and then decrease.2 Leaf stay-green characteristics of super-high-yield summer maize and nitrogen regulation2.1 Leaf stay-green characteristics of super-high-yield summer maizeCompared to non-stay-green maize, chloroplast number of stay-green maize maintained higher in flowering to milk stage, and chlorophyll content decreased slowly in the later period. Moreover, the net photosynthetic rate of ear leaf of stay-green maize dropped slowly, and owned higher photosynthesis potential, maximum photochemical efficiency(Fv/Fm) and the actual photochemical efficiency(ΦPSⅡ) during 15-45 days after flowering stage. The activity of the SOD, POD, APX in leaves of DH661 was decreased slowly than ZJ2, and the MDA activity of DH661 was lower than ZJ2 during the whole growing stage, so we can concluded that leaves of stay-green maize owned higher anti-aging ability, stronger reactive oxygen species metabolism ability and higher activity of nitrogen metabolism enzyme, but lower MDA degree. The activities of nitrogen metabolism enzymes in leaves of DH661 including NR, GS, GOGAT, GDH was performed much better than ZJ2. 2.2 Nitrogen regulation on leaf stay-green characteristics of different super-high-yield summer maizeAfter nitrogen regulation, the changes of photosynthesis potential, photosynthetic characteristics, lodging resistance and nitrogen metabolic enzymes of non-stay-green maize were significant greater than that of the non-stay-green maize. Under no fertilizer condition, organelles like chloroplast envelope and chloroplast grana were incomplete, and volumes and the amounts of the osmiophilic granules were more than the fertilizer treatments. Chloroplast structure grow deformity and chloroplast membranes uneven and begin to dissolve. That was all unfavorable for the maintenance of leaf function for no fertilizer and excessive fertilizer. In conclusion, contract to non-stay-green maize, the stay-green maize with higher yield potential have advantage in maintenance leaf function. There were significantly difference in different treatment of leaf characteristic after applying nitrogen fertilization, but no fertilizer and excessive nitrogen fertilizer were bad to maintenance leaf function. Planting the stay-green maize in testing area and applying 310-395 kg N·hm-2, income can be achieved 23000-23250 yuan·hm-2 if only consider corn grain(1.8 yuan·kg-1) and urea(1.6 yuan·kg-1).
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