There are two morphogenic pathvways in plant regeneration. These are adventitious shoot and root formation (organogenesis) and somatic embryo formation (embryogenesis). To establish a rice (Oryza sativa L.) culture system, in which highly-frequency of either organogenesis or embryogenesis were achieved, effective regeneration media were investigated. We tested N6 medium containing 20 g·l-1 sucrose, 35 or 50 g·l-1 sorbitol, 3 g·l-1 casein hydrolysate, lO mM L-proline, 10 g'l-1 agarose and different levels of abscisic acid (ABA), auxin, and cytokinin for regeneration. In our culture system, the type of cytokinin was the key to control the morphogenic pathways. One of the most active urea cytokinins, N-(2- chloro- 4- pyridyl)-N' -phenylurea (4PUCl), tended to induce adventitious shoots. A purine cytokinin, kinetin, in low concentration tended to induce somatic embrvos.
