Distribution of Cytokinin-active Ribonucleosides in Wheat Germ tRNA Species.

The distribution of cytokinin activity in wheat (Triticum aestivum) germ tRNA fractionated by BD-cellulose and RPC-5 chromatography has been examined. As in other organisms, the cytokinin moieties in wheat germ tRNA appear to be restricted to tRNA species that would be expected to respond to codons beginning with U. Only a few of the wheat germ tRNA species in this coding group actually contain cytokinin modifications. Cytokinin activity was associated with isoaccepting tRNA(Ser) species and with a minor tRNA(Leu) species from wheat germ. All other wheat germ tRNA species corresponding to codons beginning with U were devoid of cytokinin activity in the tobacco callus bioassay.