中文摘要：

【目的】测定不同水稻品种对外界铵浓度（Ammonium ion,NH4＋）的响应,通过分析不同水稻品种在不同NH4＋浓度下的表型差异及NH4＋吸收特性,揭示水稻品种间氮利用差异的机理。【方法】采用水稻品种齐粒丝苗（QLSM,氮高效品种）和沪科3号（HK3,氮低效品种）,以营养液培养方式在苗期进行3种不同NH4＋浓度（低、中、高）处理,15 d后分析两个水稻品种的株型特征、氮含量和氮积累量、根系活力及根系呼吸强度,并采用扫描离子选择电极技术分析根系NH4＋流通量。【结果】氮高效品种QLSM在低NH4＋条件下生长较好,其株高、分蘖与对照（CK）相比无显著差异,总干物质重和根部氮积累量分别增加25.9%和74.2%。氮低效品种HK3的株高、分蘖、总干物质重及根部N积累量则显著降低,降低幅度分别为10.1%、26.4%、19.5%和2.3%;此外,与CK相比,低NH4＋条件显著降低QLSM和HK3的地上部和根部氮浓度。同时,低NH4＋条件使2个水稻品种的根系活力分别降低76.0%和78.2%,根系呼吸强度分别降低29.5%和33.8%,说明水稻并未通过提高根系活力或者根系呼吸强度增加水稻在外界低NH4＋浓度下对NH4＋吸收;进一步研究表明,在低NH4＋条件下,QLSM的根系分生区有较强的NH4＋吸收,而HK3对NH4＋不敏感,其净流入量显著偏低。【结论】氮高效水稻品种QLSM低NH4＋条件下较高的NH4＋吸收利用能力与其根系分生区较高的NH4＋流入量有关。

英文摘要：

【Objective】Two rice varieties were exposed to different levels of external ammonium ion（NH4＋） condition to examine the responses and its differences. The research will further reveal the mechanisms of nitrogen use efficiency（NUE） in different absorption properties by analyzing different performances and absorption characteristics.【Method】Two rice varieties of QLSM（High-NUE） and HK3（Low-NUE） were cultivated hydroponically,and then treated with 3 NH4＋ concentrations（Low,Middle,High） for 15 days at tillering stage. Furthermore,the morphological characteristics,nitrogen content,nitrogen accumulation,root activity,root respiration and root transmembrane NH4 ＋ fluxes were determined.【Result】The results showed that QLSM grew well under low NH4＋ condition and showed no significant difference with its control in plant height and tillers. It showed that the total dry matter weight and root N accumulation increased by 25.9% and 74.2% in QLSM,respectively. Whereas,low NH4＋ condition significantly reduced plant height,tillers,total dry matter weight and root N accumulation of HK3 by 10.1%,26.4%,19.5% and 2.3%,respectively. Furthermore,compared with CK,N content in roots and shoots of the two varieties decreased under low NH4＋ condition. Meanwhile,the root activity of QLSM and HK3 sharply reduced by 76.0% and 78.2%,and the root respiration intensity also significantly decreased by 29.5% and 33.8%. The results suggested that root activity and root respiration intensity did not contribute to NH4＋ absorption under low NH4＋ condition. Moreover,under the condition of low NH4＋,NH4＋ influx was more pronounced in QLSM,while HK3 showed NH4＋ insensitivity in the root meristem zone.【Conclusion】It is concluded that high NH4＋ absorptive capacity under low NH4 ＋ is associated with enhanced NH4＋ influx in the root meristem zone.