Which of the following is not a bioassay for cytokinins?

Cytokinins have the ability to retard the degradation of chlorophyll in excised leaves. Hence, chlorophyll preservation test is a bioassay for cytokinin. Cytokinin promotes cell enlargement in the leaf tissues of certain plants. So, radish and bean leaf test have been used as bioassay. Promotion of lettuce seed germination forms the basis for another bioassay for cytokinins. Dwarf maize test is a bioassay for gibberellins as they induce internodal growth in genetically dwarf varieties of plants like pea and maize.