氮素形态对烟苗根系生长及碳、氮积累的影响

为探讨烤烟幼苗生长、根系发育及碳氮积累对不同氮素形态的响应,选用烤烟品种NC55,在水培条件下设置相同氮浓度的全铵(NH₄⁺:NO₃^-=100:0)、铵硝各半(NH₄⁺:NO₃^-=50:50)和全硝(NH₄⁺:NO₃^-=0:100)3个处理,测定不同处理的干物质积累、根系形态、烟株碳氮含量及碳氮积累量。结果表明,地上部分生物量和总生物量在不同处理时间均表现为全硝处理> 铵硝各半处理> 全铵处理。处理后7 d和14 d,根系生物量、总长度、总体积、总表面积以及各器官的碳、氮积累量和总氮积累量表现为全硝处理> 铵硝各半处理> 全铵处理;处理后21 d,上述指标表现为铵硝各半处理> 全硝处理> 全铵处理。铵态氮肥作为单一氮源抑制了烤烟生长,硝态氮肥有利于地上部生长和碳积累,但长时间作为单一氮源根系生长缓慢,铵硝混合态氮素更有利于根系的生长发育和碳氮积累。

Effect of Nitrogen form on Root Growth and C and N Accumulation of Flue-cured Tobacco Seedlings

In order to investigate the response of root growth, C and N accumulation of flue-cured tobacco seedlings to different nitrogen forms, hydroponic experiments were conducted by supplying equal amount of N in three different ratios of NH₄⁺:NO₃^- (100:0, as 100-0AN; 50:50, as 50-50AN; 0:100, as 0-100AN) to seedlings of flue-cured tobacco cultivar NC55. Plant dry biomass, root morphology, C and N content, C and N accumulation were assayed during the cultivation. The results showed that shoot and total biomass showed 0-100AN> 50-50AN> 100-0AN at all treating times. On 7 and 14 d, root biomass, root total length, root total volume, root total surface area, C and N accumulation of root, stem, leaf and total nitrogen accumulation showed 0-100AN> 50-50AN> 100-0AN. On 21 d, the same parameters showed 50-50AN> 0-100AN> 100-0AN. Ammonium as sole nitrogen source inhibited flue-cured tobacco growth. Nitrate is beneficial to shoot growth and carbon accumulation, it however inhibits root growth as sole nitrogen source for prolonged time. Optimum nitrogen form for root development, C and N accumulation is the mixture of ammonium and nitrate.