<正>以蝴蝶兰叶片为外植体，建立了蝴蝶兰植株再生系统。结果表明：（1）可通过花梗节芽建立丛生芽诱导体系，获得大量无菌材料，丛生芽诱导增殖的最佳激素组合为7.5rag/L6-BA+1.0mg/LNAA；（2）植物激素显著影响叶片类原球体的诱导，在10.0mg/L6-BA+1.0mg/LNAA的激素组合处理下，各品种的诱导效果最好；（3）4种基本培养基中.1/2MS和Hyponex对类原球体的增殖和分化效果较好；（4）蔗糖浓度对类原球茎分化成苗的影响可用y=0.01992x2+0.07751x+0.17进行拟合，在蔗糖浓度为20g/L时，蝴蝶兰类原球茎分化率达最高。

So as to abstract triterpenoids in betula, we set up spectrophotometric methods to determine the grand totalof the triterpenoids in betula bark. Vanillirr-perchloric acid, glacial acetic acid react with betulin,served as detect sample to determine the grand total of the triterpenoids. The result of experiment showed that the maximum absorption of the system is 551 nm,the temperature of coloring is 70℃, reaction time is 15 min. The linear regression equation is A=9. 198 5C+0. 015 8, r=0. 998 8. Linear range at 1. 0 X 10-2～3. 0～10-2 μg/L. Detection limit is 1. 0 × 10-5μ g/L. The precision RSD is 2. 16%. The rate of recovery is 96. 16%～98. 85%.