施氮量和种植密度对优质晚稻稻米品质的调控效应及其机制

Regulatory effects of nitrogen and density interaction on grain quality of high-quality late rice and its mechanism

以‘玉针香’为材料,设计4个施氮量处理,分别为N1(不施氮)、N2(尿素180 kg/hm^(2))、N3(尿素126kg/hm^(2))、N4(180 kg/hm^(2)尿素+生物炭200 t/hm^(2)),2个种植密度处理,分别为D1(18 cm×25 cm)、D2(14 cm×25 cm),于2020—2021年开展大田试验,研究施氮量、种植密度及其互作对稻米品质与叶片氮代谢特征的影响。结果表明:种植密度对稻米出米率、直链淀粉含量、胶稠度、蛋白质组分均无显著影响,D2处理各指标均略高于D1处理;施氮提高了出米率与各蛋白质组分含量,降低了垩白粒率和垩白度,以N4处理的效果最好;施氮量与种植密度互作对稻米品质影响显著,N4D2处理的稻米加工品质与外观品质最优,胶稠度最长,蛋白质组分含量最高;种植密度对叶片含氮量、硝态氮含量以及硝酸还原酶(NR)、亚硝酸还原酶(NiR)活性均无显著影响;D2处理的叶片含氮量以及NR、NiR活性较高;施氮提高了叶片全氮含量、硝态氮含量以及NR、NiR活性,以N4处理的最高;相关性分析结果表明,叶片全氮含量、NR活性、NiR活性与整精米率、直链淀粉含量、胶稠度、蛋白组分含量呈显著或极显著正相关,与垩白粒率和垩白度呈显著或极显著负相关;增施生物炭可显著提高整精米率,显著降低垩白度和垩白粒率。本试验条件下,N4D2处理对优质稻稻米品质的调控效应最好,其调控机制在于提高了叶片全氮含量和氮代谢酶活性。

In order to understand the regulatory effect and mechanism of nitrogen application rate and density on the quality of high-quality late rice,Yuzhenxiang was used as material to conduct field experiment under four nitrogen application rates including no nitrogen(N1),180 kg/hm^(2) urea(N2),126 kg/hm2 urea(N3),180 kg/hm^(2) urea+200 t/hm^(2) biochar(N4)and two densities including 18 cm×25 cm(D1),14 cm×25 cm(D2),and the rice quality and leaf nitrogen metabolism characteristics were collected for further comparative analysis for each treatment.The results showed that density had no significant effect on head rice yield,amylose content,gel consistency and protein fraction,and the indexes of D2 treatments were slightly higher than those of D1 treatments.Nitrogen application increased head rice yield and protein content,reduced chalkiness grain rate and chalkiness,and N4 treatment had the best effect.The interaction effect of nitrogen application rate and density on rice quality was significant,and N4D2 treatment had the best processing quality and appearance quality,the longest gel consistency and the highest protein fraction content.Density had no significant effect on leaf nitrogen content,nitrate nitrogen content,nitrate reductase(NR)and nitrite reductase(NiR)activities,while D2 treatments had slightly higher leaf nitrogen content,NR and NiR activities.Nitrogen application increased leaf nitrogen content,nitrate nitrogen content,NR and NiR activity,and N4 treatment was the highest.The correlation analysis showed that leaf nitrogen content,NR and NiR activity were significantly or extremely significantly positively correlated with head rice rate,amylose content,gel consistency and protein fraction content,and significantly or extremely significantly negatively correlated with chalkiness grain rate and chalkiness.Increasing biochar application could improve rice quality,mainly by increasing head rice rate and decreasing chalkiness and chalky grain rate.In the studied conditions,N4D2 treatment had the best regulatory effect on the quality of high-quality rice,and its regulatory mechanism was to improve the nitrogen content in leaves and the activity of nitrogen metabolism enzymes.