Conversion of N6-isopentenyladenine to zeatin by Actinidia tissues.

Tissue cultures grown from stem explants of three Actinidia species and a hybrid species rapidly converted N6-isopentenyladenine (i6Ade) to zeatin (io6Ade), a potent hydroxylated cytokinin. Within 24 h on 50 uM i6Ade, callus tissues of A. chinensis x arguta accumulated 83 +/- 6 nmol/g io6Ade which was purified using HPLC and identified by its characteristic UV and mass spectra. Activity converting i6Ade to io6Ade was also demonstrated in stem segments from intact plants where it was low in the tip (3 cm), highest in the region corresponding to rapid leaf growth and very low in the mature stem. Root segments converted i6Ade to io6Ade almost as rapidly as the most active region of the stem while leaf petioles produced little io6Ade. Fruits of A. arguta and A. chinensis produced little or no io6Ade, respectively.