METABOLISM AND TRANSLOCATION OF EXOGENOUS ZEATIN RIBOSIDE IN GERMINATING-SEEDS AND SEEDLINGS OF ZEA-MAYS

High specific activity [H-3]-zeatin riboside (ZR) was supplied to germinating seed and developing seedlings of Zea mays to study its metabolism and translocation. The major metabolites of ZR in endosperm, embryo, and first leaves were adenosine, adenine, and adenine nucleotide. When ZR was supplied to the radicle tip a significant proportion of the radioactivity extracted from the radicle was identified as zeatin-9-glucoside (Z9G). However, some ZR was also transported to the shoot and vestigial embryo. During the initial stage of germination, movement of zeatin riboside from the embryo to the endosperm was pronounced but little movement occurred in the reverse direction.