Cytokinin activity in Japanese persimmon fruits (cvs. Fuyu and Hiratanenashi) was studied with bioassay using tobacco callus (Nicotiana tabacum, cv. Wisconsin No. 38), and relationships between levels of endogenous cytokinins and fruit development were observed.
Activity in Fuyu and Hiratanenashi persimmon gradually decreased prior to bloom. The activity in pollinated Fuyu fruit increased markedly until 30 days after flowering, whereas the activity in the non-pollinated fruit remained very low during the same period. All the non-pollinated fruit dropped toward the end of June. Actvity in both pollinated and non-pollinated Hiratanenashi fruits continued to decrease after flowering. Sixty days after flowering activity in both cultivars almost completely disappeared.
Activity in the calyx of both cultivars was much lower than in the fruit and diminished quickly after flowering.
Zeatin and other unknown substances were supposed to be responsible for the activity in the crude extract of Fuyu fruit.
Levels of cytokinin compounds in persimmon fruits seem to be closely related to the growth at early stages, especially in pollinated Fuyu, but probably have no influence 60 days after flowering in both cultivars.
The differences in cytokinin activity between Fuyu and Hiratanenashi at early stages of fruit development would be of interest for further study.