Aechmea victoriana var discolor L. B. Foster and Aechmea dactylina Bal. are commercially propagated in vitro through lateral shoot growth. A modified Murashige and Skoog medium is used which contains both BA and IAA. These growth substances were shown in the present study to synergistically stimulate the production of ethylene by the cultured plants. The stimulation of ethylene production is correlated with the outgrowth of the lateral buds. The rise in ethylene production was concluded to induce lateral shoot growth, because: (a) outgrowth of the shoots was blocked by preventing an increase in ethylene production, (b) 1-aminocyclopropane-1-carboxylic acid (ACC), the natural precursor of ethylene biosynthesis, substituted for IAA in the promotion of ethylene production and lateral bud outgrowth. Although ACC could substitute for IAA, it could not substitute for BA; therefore, cytokinins are concluded to be essential for lateral bud outgrowth in vitro in Aechmea. These results suggest that cytokinins and ethylene both play roles in natural lateral bud initiation and that the cytokinin function involves two stages of the process.The family Bromeliaceae is composed of tropical American genera, many of which are herbaceous epiphytes. Some of them are important ornamentals such as several Aechmea species (5). Several possibilities exist for the multiplication of bromeliads in vivo as well as in vitro (8). In vivo propagation of Aechmea through seed has been a standard practice. The plants obtained are variable and often of poor quality. Poor germination is often another problem which is associated with propagation through seed. Vegetative multiplication through suckers is too slow to be practical (22). Therefore, 'in vitro' propagation of Aechmea has become more and more widely used. To Ethylene Inhibitors. Suppression of the ethylene production was obtained by using: 5 mg/L AVG (10); 500 mg/L AIB (12, 13); 13 mg/L Co2+ (7), and for inhibition of ethylene action 66 mg/L STS (2, 17).
RESULTSAfter in vitro germination, Aechmea plants were grown on a elongation medium containing only 1 mg/L 1-NAA during a first subculture of 10 weeks. These plants were used for experiments performed during subsequent subcultures. During the second subculture the pattern of the ethylene evolution differed with the type of culture medium used (Fig. 1)