毛白杨对15N-硝态氮和铵态氮的吸收、利用及分配

以毛白杨新无性系50号插条苗为试材，应用15N示踪技术研究在相同施氮量下毛白杨(Populus tomentosa)苗木对不同形态氮素的吸收、分配及利用特性。结果表明：不同处理下毛白杨苗木在施肥1周后对肥料氮的吸收呈逐渐上升趋势，并在施肥后28d达到最大值，NO3-15N处理苗木全氮量为0.67g/株， NH4-15N处理苗木全氮量为0.60g/株；吸收NO3-15N为0.26g/株，吸收NH4-15N为0.12g/株，分别占苗木全氮的比例39.15%和19.95%。毛白杨苗木对两种氮素的利用程度差异显著，在利用率最高时期，NO3-15N利用率可达25.83%，约为NH4-15N（12.03%）的2倍。氮素在各器官中分配差异显著，总体趋势为叶﹥根﹥茎。叶中NO3-15N的分配率显著高于NH4-15N

The Absorption, Utilization and Distribution of Nitrate 15N and Ammonium 15N in Populus Tomentosa Seedlings

Effects of different nitrogen sources(NO3- ,NH4+) on the absorption, distribution and utilization of nitrogen on Populus tomentosa seedlings (clone 50) was studied by using the 15N trace technique. Results showed that the Populus tomentosa seedlings had the same nithrogen take up pattern: tissue nitrogen content grew up after fertilization, remarkbaly rising up after one week and reached peak after 28 days. Although the treatments are different, the tissue N content was about the same between 0.6 g•plant-1 to 0.67 g•plant-1. The maximum absorption of NO3-15N and NH4-15N was 0.26 g•plant-1and 0.12g•plant-1, which accounted for 39.15% and 19.95% of total nitrogen, respectively. The nitrogen use efficiency (NUE) of two nitrogen sources varied significantly. The maximum NUE of NO3-15N reached 25.83%, nearly twice of that of NH4-15N (12.03%). Hence we conclude that Populus tomentosa seedlings (clone 50) prefer to absorb NO3-. Nitrogen distribution rate changed obviously among different organs and the trend was leaf﹥root﹥stem. In the leaf, the distribution of NO3-15N was higher than that of NH4-15N.