Achimenes is a summer-flowering pot plant commonly propagated by shoot tip cuttings taken from rhizomes released from dormancy. Micropropagation was used in this study in order to establish a protocol for producing plants in winter when Achimenes are not usually available. Leaf segments, taken in August 1993, from hybrids `Flamenco', `Rosenelfe', `Bella', and `Sandra' grown in a greenhouse, were cultured on a modified Murashige and Skoog (MS) medium supplemented with 0.1 mg·liter–1 BA and 0.5 mg·liter–1; shoots proliferated without callus formation. Leaf explants taken from the proliferated shoots were placed on MS medium with 0.5 mg·liter–1 BA and 0.1 mg·liter–1 NAA for 8 weeks for further shoots proliferation. `Bella' showed vigorous growth and produced the most shoots (82) with no rhizomes, whereas `Flamenco' had the least shoots (28) along with rhizomes. Shoot tips were then transferred on MS medium supplemented with 0.5 mg·liter–1 NAA for 6 weeks where more vigorous shoots developed along with roots. Microcuttings were directly stuck ex vitro under moisture and rooted well in 4 weeks before planting in individual culture and flowered normally. These results provide the basis for a successful production of Achimenes hybrids for growth and flowering in winter months provided optimal temperature and irradiance levels are given.
Polymeric formulations of plant growth regulators (PGR) are high-molecular weight systems in which the PGR unit can be slowly released providing prolonged action and effectiveness in a wide range of concentrations. In this study, Achimene explants were used for testing the biological activity of polymeric derivatives of NAA and 2,4-D. Shoots of Achimenes `Bella', obtained from leaf segments cultured in vitro, were transferred for 8 weeks on Murashige and Skoog (MS) medium supplemented with different levels of conventional or polymeric NAA (0, 0.01, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5 mg·liter–1) and 2.4-D (0, 0.01, 0.05, 0.1, 0.5, 1.0, 1.5 mg·liter–1), each combined with three levels of BAP (0, 0.1, 0.5 mg·liter–1). Compared to conventional NAA, twice as many shoots proliferated with higher dry weight, at 0.5 0.1, 1.0, or 1.5 mg·liter–1 polymeric NAA with 0.5 mg·liter–1 BAP. In another trial, the combination of 0.05 or 0.1 mg·liter–1 polymeric 2,4-D with 0.1 BAP gave more shoot and vigorous growth without callus formation, compared to conventional 2.4-D These results suggest that the polymeric derivatives of auxins used in this study enhance regeneration and growth of Achimenes in vitro more effectively than conventional formulations, at greater concentrations, without causing toxic or inhibitory effects.