Portulal: a rooting promoting substance in Portulaca leaves

A new bioassay which employs disbudded epicotyl cuttings takenfrom light grown Azukia seedlings (A. angularis) was devisedfor testing rooting promotion activity. By use of this method,the rooting promoting principle in leaves of Portulaca grandiflorawas isolated and identified with portulal which had been previouslyobtained. Portulal was reported as an inhibitor of rooting inetiolated Raphanus cuttings and has recently been determinedto be a bicyclic diterpene containing a perhydroazulene nucleus.Portulal promoted the adventitious root formation in severalkinds of plants, i.e. Azukia angularis, Vigna Catiang var. sinensis,Phaseolus Mungo and Raphanus sativus var. acanthiformis ‘Risodaikon’. The rooting process in Azukia and Raphanus cuttings seems toinclude at least two phases; a "preparatory phase" or a portulal-and gibberellin-sensitive phase and a "main phase" or an auxin-sensitiveand portulal-insensitive phase. ¹Contribution No. 16 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Tokyo, Japan. (Received April 3, 1969; )