To study the relationship between the varietal difference in flower longevity and natural occurring cytokinins, 18 g fresh
weight of petals from young flowers of Lovita and Golden Wave were extracted and purified as above. The concentrate was made up to 3.5 ml with water, and 0.1 ml was applied to 4.5-cm wide strips of Whatman 3MM paper. Thirty paper strips were prepared from each extract and were developed by ascending chromatography with isopropanol-ammonium hydroxide-water (8:1:1, v/v) as a solvent. After drying, each paper strip was cut into 10 equal zones. Two corresponding zones from the paper strips served as one replicate, so that 15 replicates were used for each RF zone. Soybean callus pieces (about 7-10 mg) were placed individually on agar in a test tube (23 X 100 mm) containing the two zone papers and 12 ml of Miller's medium (11). The tissue cultures were kept in darkness at 27 C and harvested after 4 to 5 weeks. Kinetin equivalents were calculated from standard curves obtained separately for each test.