Abstract
The diphenylurea derivative thidiazuron induces a variety of cytokinin responses. Levels above 5 x 10(-9) molar and 4 x 10(-7) molar stimulate maximum soybean callus growth and radish cotyledon expansion, respectively. A wider range of dose response related effects follows thidiazuron induced tobacco plant regeneration. Analysis of soybean callus extracts strongly suggests that thidiazuron treatment creates an accumulation and/or synthesis of purine cytokinins, able to induce the growth, expansion and regeneration, mentioned above.