【摘要】 目的:探讨氮素形态对喜树幼苗喜树碱含量及其生物合成途径中色氨酸合酶（TSB）和色氨酸脱羧酶（TDC）活性的影响。方法:在温室内对砂培喜树幼苗进行5种NH_<sup>+-N/NO₃^-N比例的处理,用HPLC检测了幼叶中喜树碱含量和TSB活性以及茎皮中TDC活性的动态变化过程。结果:喜树碱含量与氮素形态有明显的关系,NH₄⁺- N/NO₃^--N为25:75时最有利于喜树碱在幼叶中的合成和积累（最高值达5.69‰）,且在处理的前30 d呈上升趋势而随后下降。幼叶中TSB活性与氮素形态关系不十分明确。NH₄⁺-N/NO₃^--N为25:75时茎皮的TDC活性最大,并且TDC活性的变化与幼叶的喜树碱含量相关。结论:适宜的氮素形态比例对喜树幼苗中喜树碱的积累极为重要,短期NH₄⁺-N/NO₃^--N为25:75的处理可通过上调茎皮中TDC活性诱导幼叶中高含量的喜树碱。更多还原

【Abstract】 Objective:To investigate the effects of nitrogen forms on the camptothecin（CPT）content,tryptophan synthase（TSB） and tryptophan decarboxylase（TDC）activities in Camptotheca acuminata seedlings,Method:The seedlings of C.acuminata with 6 pairs of leaves were subjected to 5 different NH₄⁺-N/NO₃^--N ratio（0:100,75:25,50:50,25:75,100:0）treatments by sand culture in a greenhouse. The CPT content,TSB activity in the young leaves and TDC in the stem barks of the seedlings were determined by HPLC on the 15th,30th, 45th,60th and 75th day,respectively.Result:The obvious relationship between CPT content and nitrogen forms was observed.When NH₄⁺- N/NO₃^--N ratio was 25:75,CPT accumulation in young leaves displayed the best advantages（the highest value is 5.69‰）and increased in the early 30 days of treatment and then declined.There was no obvious relationship between TSB activity in the young leaves and nitrogen forms.TDC activity in the stem bark was the highest when NH₄⁺-N/NO₃^--N ratio was 25:75,and the change of TDC activity paralleled to CPT content in the young leaves.Conclusion:A short-term treatment that NH₄⁺-N/NO₃^--N ratio was 25:75 may gain high CPT content in the young leaves through enhancing the TDC activity in the stem bark of C.acuminata seedlings.更多还原