中文摘要：

采用控制条件下的水培试验,对不同氮形态（全铵、铵硝混合（75：25）、全硝营养）条件下水稻苗期的氮素吸收和根系生长进行了研究。结果表明：铵硝混合营养条件下水稻的生物量和氮素积累量最高,全铵和全硝营养之间差异不明显。铵硝混合营养处理的水稻地上部和根系的氨基酸含量最高,全铵处理次之,全硝处理最低。全硝处理的水稻植株硝酸盐含量约为全铵和铵硝混合处理的4倍,铵硝混合营养处理的水稻植株硝酸盐含量高于全铵处理,增幅为18%。培养时间为0～5 d时,铵硝混合和全硝处理的水稻根系总长差异不明显,但高于全铵处理。从第5天开始,铵硝混合和全铵处理的根系总长增加迅速,培养到7 d时水稻的根系总长已显著大于全铵和全硝处理,增幅约为35%。全铵和全硝处理的水稻根系总长差异不显著。不同氮形态处理的水稻根系总长变化主要是由侧根总长的变化引起的,而侧根数的变化是侧根总长变化的主要原因。

英文摘要：

Hydroponic experiments were conducted to study the effects of different ratios of NH＋4 to NO-3（NH＋4：NO-3 as 100：0,75：25 and 0：100）on N uptake and root morphology in rice（Oryza sativa L.）at the seedling stage.The results obtained were as follows：Higher biomass and N accumulation were found in the mixed solution of NH＋4 and NO-3 while no difference was found between sole NH＋4 and NO-3 solution.Amino acid content in the mixed solution of NH＋4 and NO-3 was the highest and that in sole NO-3 solution was the lowest.Nitrate content in sole NO-3 solution was four times of that under two ratios of NH＋4 to NO-3（100：0 and 75：25）.And mixed NH＋4 and NO-3 solution increased NO-3 content by 18% compared to sole NH＋4 solution.From 0 to 5 d,total root length was similar to that under two ratios of NH＋4 to NO-3（75：25 and 0：100）,which was higher than that in sole NH＋4 supply.After 5 d,total root length markedly increased under two ratios of NH＋4 to NO-3（100：0 and 75：25）.Mixed NH＋4 and NO-3 solution increased total root length by 35% compared with sole NH＋4 and NO-3supply while there no obvious difference between sole NH＋4 and NO-3 supply.The change of total root length was mainly resulted from total lateral root length which was affected by lateral root initialing.