氮肥运筹对糜子生育后期干物质积累与转运及叶片氮素代谢的调控效应

【目的】通过分析不同氮肥水平对糜子干物质积累、转运及生育后期功能叶片氮素代谢的影响，探讨糜子干物质积累、转运特征和氮代谢变化规律，为糜子节肥增产提供理论依据。【方法】采用大田试验，以榆糜2号为试验材料，设置60 kg·hm^-2（N1）、105 kg·hm^-2（N2）、150 kg·hm^-2（N3）、195 kg·hm^-2（N4）4种不同施氮水平，以不施肥为对照（CK）。连续两年研究了糜子抽穗期、开花期、灌浆期和成熟期干物质积累、转运及产量变化，分析了不同氮肥条件下，糜子旗叶、倒二叶和倒三叶叶片的谷氨酰胺合成酶（GS）活性、硝酸还原酶（NR）活性、游离氨基酸含量和可溶性蛋白含量以及籽粒中含氮量、蛋白质含量等氮素代谢指标的变化规律，进一步研究了不同氮肥水平下糜子产量及产量构成因素的变化，总结了糜子干物质积累特性、叶片氮素代谢与产量的相关性。【结果】试验结果表明，随着施氮量的增加，糜子不同器官的地上部干重呈先上升后下降的趋势，开花期糜子N3（150 kg·hm^-2）处理下的茎干重、叶干重、鞘干重和穗干重最大，分别比不施肥（CK）提高了51.2%、40.8%、64.2%和41.3%；氮肥处理促进了糜子抽穗后植株干物质在不同器官中的移动与转运，提高了地上部器官对籽粒的贡献率。其中，N3（150 kg·hm^-2）处理下的叶干物质移动率比不施肥提高了9.6%，转运率提高了12.4%；氮肥处理下的糜子不同叶位叶片GS活性、NR活性、游离氨基酸含量以及可溶性蛋白含量均表现出先上升后下降的变化趋势，但施氮不影响糜子生育期内叶片氮素代谢的整体变化规律。同一生育时期，糜子顶3叶叶片GS活性、NR活性、游离氨基酸含量以及可溶性蛋白含量均表现为旗叶＞倒二叶＞倒三叶，N3（150 kg·hm^-2）处理下达到最大值；氮肥处理下的糜子籽粒含氮量比不施肥分别提高了4.0%、6.0%、7.8%和8.9%；不同处理籽粒蛋白质含量变化趋势基本一致，分别较不施肥增加3.89%、5.75%、7.54%和8.59%，并且差异均与CK达到显著水平。氮肥处理显著增加了糜子穗长、茎粗、单株穗数和千粒重及产量，2015年，不同氮肥处理条件下的糜子产量较不施肥分别增加10.09%、29.71%、44.73%和35.99%；2016年分别增加19.08%、30.60%、65.85%和39.14%。两年试验条件下，N3（150 kg·hm^-2）处理的糜子产量增加比例均最大，增产效果最好。【结论】适宜的施氮量可促进糜子干物质积累与转运，有利于改善生育后期糜子叶片的氮素代谢，延缓了叶片的衰老，提高糜子产量。本试验条件下，陕北地区糜子生产的最佳氮肥施用量为150 kg·hm^-2。

Effects of Nitrogen Fertilizer on Dry Matter Accumulation,Transportation and Nitrogen Metabolism in Functional Leaves of Broomcorn Millet at Late Growth Stage

【Objective】 The propose of this study was to investigate the basis of nutritional requirement and supply on high quality of broomcorn millet through studying structure characteristics of dry matter and regularity of nitrogen metabolism in functional leaves of broomcorn millet at late growth stage under different nitrogen levels.【Method】Broomcorn millet cultivar of Yumi2 was selected as the material in a field experiment from 2015 to 2016. Dry matter accumulation, distribution and transportation were conducted at heading stage, flowering stage, filling stage and maturity stage under different nitrogen levels of 60 kg·hm^-2 (N1), 105 kg·hm^-2 (N2), 150 kg·hm^-2 (N3), 195 kg·hm^-2 (N4), and glutamine synthetase (GS) activity, nitrate reductase (NR) activity, free amino acids and soluble protein content in functional leaves were detected, as well as yield and yield components were analyzed. The correlation between the dry matter accumulation, transportation of broomcorn millet and nitrogen metabolism of the leaves or yield were summarized.【Result】The results showed that the accumulation of dry matter of above-ground organs increased with increasing N application rates up to 150 kg·hm-2, and then decreased when N application rate was 195 kg·hm^-2. The stem dry weight, leaves dry weight, sheath dry weight and spike dry weight under N3 treatment increased 51.2%, 40.8%, 64.2% and 41.3%, respectively, compared with the non-fertilization treatment at the flowering stage. Transportations of dry matters in different organs were improved by applying nitrogen fertilizer. Distribution rate of aboveground organs were increased to grain after heading, which increased 9.6% under N3 treatment, compared with the non-fertilization treatment. The GS activity, NR activity, free amino acid and soluble protein content in different leaves were upward-declined under nitrogen treatment. Nitrogen metabolism activities were the flag leaves > the second leaves >the third leaves at the same period, among them, N3 treatment reached the maximum value, but the overall change of nitrogen metabolism was not affected in functional leaves. Compared with no nitrogen application, the nitrogen content of grain under N1, N2, N3 and N4 treatments increased by 4.0%, 6.0%, 7.8% and 8.9%, respectively, and the protein content of grain by nitrogen fertilizers were significantly increased by 3.89%, 5.75%, 7.54% and 8.59%, respectively. The length of millet, the number of stalks, the number of panicles and the grain weight and the yield were also significantly increased by nitrogen fertilizer. Compared with no nitrogen application, in 2015, yield of broomcorn millet under N1, N2, N3 and N4 treatments were significantly increased by 10.09%, 29.71%, 44.73% and 35.99%, respectively. In 2016, which were significantly increased by 19.08%, 30.60%, 65.85% and 39.14%, respectively. The biggest increase in virginity was N3 treatment in two years. Therefore, N3 treatment was the best effect on increasing yield. 【Conclusion】The dry matter accumulation, transportation and nitrogen metabolism in functional leaves of broomcorn millet could be promoted by nitrogen fertilizer at late growth stage, and yield and yield components could be improved. Under this experimental condition, N3 treatment (150 kg·hm^-2) was the suitable amount of nitrogen in Yulin, Shaanxi.