Hydroxylation of N-(Delta-Isopentenyl)adenine to Zeatin: Relative Activities of Organ Systems from Actinidia arguta.

By incubating explants from Actinidia arguta seedlings on a nutrient medium supplemented with 20 to 30 micromolar N(6)-(Delta(2)-isopentenyl)adenine (i(6)Ade) and then measuring zeatin (io(6)Ade) accumulation in tissues, the distribution of i(6)Ade hydroxylase activities in whole plants could be determined. Based on analyses with three entire plants, it is estimated that, as an organ system, roots contain approximately 68% of the plant's hydroxylase, while stems and leaves account for about 26% and 6%, respectively, of the total activity. Depending on the part of the root examined, hydroxylase activities ranged from 20 to 148 nanomoles io(6)Ade accumulated per gram fresh weight per 24 hours of incubation. Stem activities ranged from 17 to 165 nanomoles per gram fresh weight per 24 hours with the lowest activities being found at the tip. Leaf activities were substantially lower (1-10 nanomoles per leaf depending on position) than either root or stem.