不同氮高效玉米品种对氮素的吸收转运和代谢研究

为研究不同氮高效型品种的氮素代谢调控机制,本试验以高氮高效型玉米品种先玉335和低氮高效型玉米品种京农科728为试材,设置5个施氮水平120、180、240、300、360 kg·hm^-2,以本地大田生产施氮量360 kg·hm^-2为对照(NCK),探讨不同基因型玉米植株氮素转运、氮代谢关键酶活性和关键酶基因表达对减施氮肥的响应特征。结果表明,当施氮量为240~300 kg·hm^-2时,先玉335各生育时期氮含量较高,平均产量达到较高水平;当施氮量为180~240 kg·hm^-2时,京农科728各生育时期氮含量较高,平均产量达到较高水平。在低氮条件下,相较于先玉335,京农科728的硝酸还原酶(NR)、亚硝酸盐还原酶(NiR)、谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)、天冬酰胺合成酶(AS)均可保持较高的活性。相较于拔节期,京农科782在大喇叭口期的NR基因相对表达量显著上调;大喇叭口至灌浆期,两品种的GOGAT1和GOGAT2基因均显著上调;抽雄吐丝和灌浆期,京农科728中的GS1-3基因相对表达量显著上调;灌浆期,先玉335的GS1-3基因表达量显著上调。相较于拔节期,在其他生育期,两品种的GS1-4基因相对表达量均显著下调。相较于拔节期,京农科728在灌浆期的AS1和AS3基因相对表达量显著上调。相较于其他各生育时期,先玉335在拔节期的AS1基因显著上调。本研究结果证明了氮代谢关键酶基因对不同氮高效型品种的氮素吸收调控存在显著差异。本研究为了解不同氮高效型品种的氮素吸收调控特征提供了理论依据。

Study on the Nitrogen Uptake and Metabolism in Different Nitrogen Efficient Maize Varieties

In order to study the regulation mechanism of nitrogen metabolism in different nitrogen-efficient varieties, the high-nitrogen high-efficiency corn variety Xianyu 335 and the low-nitrogen high-efficiency corn variety Jingnongke 728 were used as test materials. Five nitrogen fertilizer applications were tested: 120 kg·hm^-2, 180 kg·hm^-2, 240 kg·hm^-2, 300 kg·hm^-2, and 360 kg·hm^-2 (NCK). Using the local field nitrogen fertilizer application (NCK) as control, we explored the responses characteristics of different genotypes of maize on nitrogen transport, key enzyme activities, and key enzyme genes of nitrogen metabolism to reduced nitrogen fertilizer application. Our results showed that when the nitrogen fertilizer application was 240-300 kg·hm^-2, the nitrogen content of Xianyu 335 reached its maximum value at each growth stage, and yield reached a high level. When the nitrogen fertilizer application was 180-240 kg·hm^-2, the nitrogen content of Jingnongke 728 reached its maximum value at each growth stage, and yield reached a high level. Under low nitrogen conditions, compared with Xianyu 335, nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamic acid synthetase (GOGAT), and asparagine synthetase (AS) of Jingnongke 728 maintained high enzymatic activity throughout the entire maize growth period. Compared to the elongation stage, the expression of the NR gene of Jingnongke 782 was significantly increased in the flare opening stage. The expression of GOGAT1 and GOGAT2 genes of both varieties were significantly up-regulated from the flare opening stage to the filling stage. During the silking stage and the filling stage, the expression of the GS1-3 genes in Jingnongke 728 was significantly up-regulated. During the filling stage, the expression of the GS1-3 gene of Xianyu 335 was significantly up-regulated. Compared to the elongation stage, the expression of GS1-4 genes of both varieties was significantly down-regulated in other growth stages. The expression of AS1 and AS3 genes of Jingnongke 728 were significantly up-regulated in the filling stage compared to the elongation stage. Compared to other growth stages, the expression of the AS1 gene of Xianyu 335 was significantly up-regulated in elongation stage. There were differences in the response of different genes to nitrogen fertilizer at different growth stages in maize. The results of this study demonstrate that significant differences were obseved in the regulation of nitrogen uptake by key nitrogen metabolism enzyme genes in different nitrogen-efficient varieties of maize. This study provided the basis for understanding the regulate characteristics of nitrogen uptake of different nitrogen efficient varieties.