EFFECT OF AUXIN AND PHENOBARBITAL ON THE ULTRASTRUCTURE AND DIGITOXINCONTENT IN DIGITALIS-PURPUREA TISSUE-CULTURE

Callus derived from Digitalis purpurea hypocotils were grown during a 6-week period on solid Murashige-Skoog medium supplemented with 1 mg/L 6-benzylaminopurine, 0.01 mg/L gibberellic acid and 0.1 mg/L indole-3 -acetic acid or alpha-naphthaleneacetic acid, with or without phenobar bital (40 mg/L). The presence of phenobarbital in the culture medium c aused a reduction of the vacuole/cytoplasm ratio. At the same time, th e chloroplastic volume fraction decreased in callus tissue cells grown in media supplemented with phenobarbital, while the mitochondrial vol ume ratio increased. Digitoxin content was enhanced in callus tissues, especially in those grown on indole-3-acetic acid medium supplemented with phenobarbital. The relationship between ultrastructure of D. pur purea callus and digitoxin content is discussed.