Solution

The first cytokinin was isolated from herring sperm in 1955 by Miller. This compound was named as kinetin because of its ability to promote cytokinesis. Natural cytokinins are synthesized in regions where rapid cell division is occurring. e.g., root apices, developing shoot buds, young fruits etc.
Cytokinins overcome apical dominance. They promote nutrient mobilization that help in delay of leaf senescence.
Thus, the correct answer is option D.