ORIGIN OF SOMATIC EMBRYOGENESIS IS PROLIFERATING ROOT PRIMORDIA IN SEED DERIVED OAT CALLUS

The ontogeny of somatic embryos and proliferating root primordia in ti ssue cultures of mature seeds of oats is described. Callus formation w as initiated on developing embryos of mature oat seeds maintained on M urashige and Skoog's medium containing 2 mg l(-1) 2,4-dichlorophenoxya cetic acid. The root primordia on subculture medium did not elongate b ut multiplied by forming new primordia directly From root meristem, af ter callusing or by cleaving pre-existing root primordia. In the root meristem region somatic embryogenesis could also occur. The first soma tic embryos were observed at the end of the first subculture. Differen t developmental stages of somatic embryos were histologically identifi ed in the culture. Occasionally shoot buds were formed directly from r oot primordia. Among 5 tested cultivars Risto had the best response on callus culture medium. 200 shoots/plantlets per gram of a 10-month cu lture were obtained on MS germination medium containing 0.01 mg l(-1) ABA and 6% sucrose.