ROLE OF ETHYLENE ON DENOVO SHOOT REGENERATION FROM COTYLEDONARY EXPLANTS OF BRASSICA-CAMPESTRIS SSP PEKINENSIS (LOUR) OLSSON INVITRO

The promotive effect of AgNO3 and aminoethoxyvinylglycine (AVG) on in vitro shoot regeneration from cotyledons of Brassica campestris ssp. pekinensis in relation to endogenous 1-amino-cyclopropane-1-carboxylic acid (ACC) synthase, ACC, and ethylene production was investigated. AgNO3 enhanced ACC synthase activity and ACC accumulation, which reached a maximum after 3 to 7 days of culture. ACC accumulation was concomitant with increased emanation of ethylene which peaked after 14 days. In contrast, AVG was inhibitory to endogenous ACC synthase activity and reduced ACC and ethylene production. The promotive effect of AVG on shoot regeneration was reversed by 2-chloroethylphosphonic acid at 50 micromolar or higher concentrations, whereas explants grown on AgNO3 medium were less affected by 2-chloroethylphosphonic acid. The distinctive effect of AgNO3 and AVG on endogenous ACC synthase, ACC, and ethylene production and its possible mechanisms are discussed.