中文摘要：

玉米是高需氮作物，随着近几年作物经济产量的提高，施肥量投入过高导致了环境污染及作物氮肥利用率低等一系列问题。而作物苗期根系生长可以为后期的生长和经济产量提高打下坚实的基础。该研究以玉米自交系郑58和昌7-2及它们的杂交系郑单958为材料，采用液体培养方法，研究了0.02 mM、0.20 mM、2.00 mM、10.00 mM、20.00 mM（其中2 mM浓度处理为对照）硝酸盐浓度处理下三个玉米品种幼苗生物量、根系形态变化及测定硝态氮含量，结果表明：低浓度硝酸盐胁迫下，玉米幼苗侧根伸长受抑制，根系和地上部干物重受抑制，地上部的抑制作用较显著，表现为根冠比增加；高浓度硝酸盐胁迫下，玉米幼苗侧根长度和密度、根系和地上部干物重均下降，但体内的硝态氮含量则继续上升，表明这种奢侈的吸收与玉米幼苗的生长没有直接关系。子代郑单958品种幼苗的侧根长度大于亲本，体内硝态氮含量及干物质积累量也明显高于亲本，说明庞大的根系有利于吸收更多的养分，合成更多的干物质，同时也表明了子代的杂种优势。

英文摘要：

Maize crop nitrogen demand is high, with the crop yields to improved in recent years, series of environmental pollution and low use efficiency of crops caused by excessive nitrogen.The crop root growth can lay a solid foundation for growth and improving post-production. In this study,Zheng 58 maize and Chang 7-2inbred lines,and their hybrids Zheng 958 as materials, using liquid culture method to study the 0.02 mM,0.20 mM,2.00 mM,10.00 mM,20.00 mM （where 2.00 mM concentrations as control） nitrate concentrations seedling biomass,root morphology and determination of nitrate under three maize varieties content,the results showd that the concentration of nitrate at low stress, elongation of maize seedling lateral inhibition, root and shoot dry weight was inhibited,the inhibition of the more notable shoot, shoot ratio increased performance;high concentrations of nitrate under stress seedling lateral length and density, root and shoot dry weight decreased,but the nitrate content in the body continued to rise, indicating that luxury was not directly related to absorb the growth of maize seedlings.Offspring root length, vivo nitrate content and dry matter accumulation was significantly higher than that of the parent, it indicated that the huge roots help absorb more nutrients,produced more dry matter to show heterosis offspring.