A study of the hypothetical role of cytokinins in completion of tRNA

Abstract
It has been suggested that the effect of cytokinins in retarding leaf senescence comes about through their incorporation into tRNA. To test this hypothesis, kinetin-8-14C, 6-benzylaminopurine-benzyl-7-14C and adenine-8-3H were applied to detached tobacco leaves, and the nucleic acids were thereafter extracted and chromatographed on MAK columns. Kinetin-8-14C and adenine-8-3H were readily incorporated into RNA in a similar pattern. 6-Benzylaminopurine-benzyl-7-14C was effective in delaying chlorophyll loss but was not incorporated into any nucleic-acid fraction. It is concluded that the possibility of cytokinins retarding leaf senescence by completion of tRNA is not supported.