Studies on the effects of hypomethylation by 5-azaC upon plant forms and floralcolor in petunia ~i(Petunia hybrida).~i The seeds were asepic cultured onto MS mediumcontaining 0,50, 100, 200 and 400 (+,m)M 5-azaC respectively for 3 weeks and theshoot explants into MS medium contain 0, 100, 200, 400, 800 and 1600 (+,m)M 5-azaCrespectively for 3 weeks after that transferred to pots with soil and cultivatedunder natural photoperiod in the greenhouse. The seed germination of 5-azaC treatmentwere found to be nonsignificantly difference from the control and 5-azaC induced thedecreasing of the stem height and related to the level of 5-azaC concentration. Thegenomic DNAs isolated from the selected plants such as the short plants and thefloral color abnormal plants were nonsignificantly difference form that of thecontrol. The progenies were not exhibited the short plants while exhibited theabnormal floral plants to the M(,1) and M(,2). The percentage of survival plants ofthe 5-azaC treated shoot explants were reduced and related to the increasedconcentration. The results of 5-azaC-treated shoot explants were found to bereduction in stem height and induced abnormal flower the same as the 5-azaC-treatedseeds. Besides, the early-flowering plants were found.