The uptake and the transport of14C-labeled epibrassinolide in intact seedlings of cucumber and wheat

The uptake and the transport of exogenously applied epibrassinolide (EBR) in seedlings of cucumber and wheat were examined by autoradiography using14C-EBR.14C-EBR was applied to roots, young and mature leaves, and the shoot apex. When applied to roots,14C-EBR was readily taken up and was swiftly transported throughout both plant species. When14C-EBR was applied to the adaxial surface of a young cucumber leaf, it was readily taken up, but was very slowly transported. In cucumber leaves,14C-EBR was transported throughout the treated leaf after 3 days of treatment, and then it was transported to upper leaves from the treated leaf after 7 days. Some 6.3% of applied14C-EBR was transported to the newly expanded leaves. In wheat leaves,14C-EBR was transported only in the apical direction from the treated spot after 3 days of treatment, but it was not transported from the treated leaf to the other leaves or organs even after 7 days. Some 1.3% of applied14C-EBR was transported to the tip area of the treated leaf. These results indicate that exogenous EBR applied to intact plants is acropetally transported.