Janet Turner

Reversed Activities of Cytokinin Bases and Ribonucleosides in Callus Tissues of Phaseolus lunatus L.

Summary Relative activities of the free base and ribonucleoside forms of three cytokinins were compared in promoting callus growth of Phaseolus lunatus . Zeatin and N 6 -isopentyladenine were more active than the corresponding ribonucleosides. However, N 6 -(Δ 2 -isopentenyl)adenine (i 6 Ade) was less active than N 6 -(Δ 2 -isopentenyl)adenosine (i 6 Ado) in most of the genotypes examined. In two genotypes, P.I. 256845 and P.I. 260415, the activity of i 6 Ade was higher than that of i 6 Ado. The reversed activities of the base and ribonucleoside forms between the two groups of genotypes were not associated with differences in either the uptake or the metabolism of 14 C-i 6 Ade or 14 C-i 6 Ado. The specificity in the structural requirements of cytokinins for growth may suggest that there could be differences between the two groups of genotypes in the utilisation of these compounds.