REQUIREMENT OF ETHYLENE FOR GROWTH OF CALLUS AND SOMATIC EMBRYOGENESIS IN MEDICAGO-SATIVA L

The role of ethylene in the growth of callus and somatic embryogenesis in Medicago sativa was examined. The application of 2,5-norbornadiene, a competitive inhibitor of ethylene action, during a 10 d induction period to medium containing 2,4-D and kinetin inhibited the growth of callus but did not affect somatic embryogenesis, nor did it affect ethylene production during the induction stage. The exposure of tissue, incubated on differentiation medium, without hormones, to an atmosphere of 2,5-norbornadiene, inhibited both growth and embryo maturation and stimulated pigmentation. The inhibition of embryo maturation was observed even in the presence of norbornadiene at a concentration which did not affect growth of tissue. It is suggested that the action of endogenous ethylene is necessary for the growth of the callus and embryo maturation.