Role of Ethylene and Cytokinins in the Initiation of Lateral Shoot Growth in Bromeliads

Abstract

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)

The Protein Kinase SnRK2.6 Mediates the Regulation of Sucrose Metabolism and Plant Growth in Arabidopsis

“…4) is contradictory with the role of SnRK2.6 as a positive regulator of ABA signaling. This is because ABA moderately represses lateral bud outgrowth (Cline and Oh, 2006), whereas ethylene and cytokinins stimulate lateral bud formation (Van Dijck et al, 1988). In addition, SnRK2.6 overexpression resulted in a greater petiole upward movement, and such hyponastic response was augmented in response to attack by the powdery mildew pathogen (data not shown).…”

In vitro STORAGE OF SYNTHETIC SEEDS OF Aechmea fasciata

“…Therefore, in vitro propagation of Aechmea has become more and more widely used. To start the in vitro multiplication of Aechmea, plantlets can be obtained from in vitro germination or from explanted shoot-tips or axillary buds (Van Duck et al, 1988). Synthetic seed technology could be useful in conservation of clonal germplasm of elite and endangered plants in near future, with development of appropriate storage techniques (Naik and Chand, 2006).…”

DWARF27, an Iron-Containing Protein Required for the Biosynthesis of Strigolactones, Regulates Rice Tiller Bud Outgrowth

“…However, a large body of evidence suggests that auxin cannot directly enter the axillary buds and that a second messenger is required to inhibit the outgrowth of axillary buds (Shelagh and John, 1975;Morris, 1977;Pilate et al, 1989;Prasad et al, 1993;Booker et al, 2003). Cytokinin is the first reported second messenger candidate, which is synthesized in roots and transported acropetally in the xylem to promote directly the outgrowth of axillary buds (Van Dijck et al, 1988;Cline, 1991;Eklof et al, 1997;Kapchina-Toteva et al, 2000;Nordstrom et al, 2004). Exogenous application of cytokinin to axillary buds promotes their outgrowth (Sachs and Thimann, 1964;Cline, 1991).…”