Promotive effects of endogenous and exogenous cytokinins on the growth of cucu Cytokinin activity in decreasing order was: N6-benzyladenine (BA), N6-isoamyl adenine (iso Am), DELTA-2-isopentenyladenine (2iP), trans-zeatin (t-Z), cis-zeatin (c-Z) and kinetin (K). The endogenous cytokinin levels in the cucumber fruits were examined in relation to fruit growth using the Amaranthus assay. The increase in the amounts of the cytokinins corresponding to zeatin in extracts as bioassay on paper chromatogram coincided with the increase in fresh weight, suggesting promotive effect of the endogenous cytokinins for fruit growth.