Cytokinin activity in Lupinus albus

Abstract

The distribution and metabolism of {8‐14C}zeatin incorporated into the transpiration stream of fruiting white lupin plants (Lupinus albus L.) has been studied. The distribution pattern of 14C in the different aerial organs suggests that the amount of cytokinin being incorporated into any one organ may have been a function of its transpiration rate. Once in these organs, particularly the leaves, zeatin was rapidly metabolised and or utilised. This resulted in the formation of a number of labelled compounds that did not give a response with the soybean callus bioassay. Substances co‐eluting with zeatin glucoside and ribosylzeatin appeared to be the principal biologically active metabolites. From the present evidence it can be concluded that the leaf and side shoots received a major proportion of the applied labelled cytokinin. However, the presence of a small amount of radioactivity co‐eluting with zeatin and ribosylzeatin in the fruits indicates that the high levels of cytokinins normally associated with these organs need not necessarily all have been synthesised in situ.