中文摘要：

为给弱筋小麦优质栽培提供凭据,在大田条件下,以弱筋小麦宁麦9号为材料,测定小麦各生育期植株氮、可溶性糖含量以及籽粒产量和品质,研究种植密度及氮肥运筹对植株碳氮代谢变化和籽粒品质的影响。结果表明,植株体内含氮量在越冬始期最高,随生育进程的推移而逐渐下降,可溶性糖含量在越冬始期、孕穗-开花期含量较高,拔节期含量较低,C/N比值与糖含量变化趋势相似。拔节、孕穗、开花期植株糖含量及糖氮比与籽粒淀粉含量呈显著正相关。适当降低施氮量、减少后期施氮比例及提高种植密度,能显著提高生育中后期植株可溶性糖含量及C/N比值,降低生育后期植株含氮量,减少氮素的吸收积累,降低花后14-35 d硝酸还原酶（NR）活性,从而降低籽粒蛋白质含量,改善弱筋小麦品质。在本试验条件下,种植密度为240万/ha,施氮量240 kg/ha,氮肥运筹比例为7∶1∶2（基肥∶壮蘖肥∶倒二叶肥）时,各生育时期碳氮含量和碳氮比值均较适宜,易于实现弱筋小麦高产优质。

英文摘要：

Effects of plant density and nitrogen fertilizer on carbon and nitrogen metabolism of weak-gluten wheat variety Ningmai 9 were studied.N content in plants reached its peak at the beginning of over-wintering,then gradually decreased with growth and development.Total soluble sugar content was high at over-wintering,booting and anthesis stage,but low at the jointing stage.The change of C/N ratio was similar to that of total soluble sugar content.Total soluble sugar content and C/N ratio in plants at jointing stage,booting stage and anthesis were significantly positively correlated with grain starch content.Decreasing N application amount or its rate after jionting stage or increasing plant density could obviously increase total soluble content and C/N ratio after jionting stage,decreasing N content in plant after jionting stage and nitrate reductase activity in flag-leaves from the 14th to 35th DAA,which resulted in the decrease of grain protein content and the improvement of weak gluten wheat quality.The treatment of 240×10^4 plants/ha density,240 kg/ha N and the ratio of basal∶ top dressing N 7∶3 could get high grain yield with good quality.