Initial development and in vitro growth of Cattleya violacea (Kunth) Rolfe in different sucrose concentrations

The aims of this study were to analyze the initial germination aspects and evaluate the effect of sucrose concentrations on in vitro growth of Cattleya violacea. Mature seeds from closed pods were sowed on MS (Murashige and Skoog) culture medium. The external morphology of seed and plantlets were documented by light and scanning electron microscopy. Plantlets with 90 days after sowing were subcultured on 1/2 MS (with half-strength macronutrients concentrations) culture medium with different sucrose concentrations (0, 10, 20, 30 and 40 g L-1), incubated under the same in vitro conditions during more 150 days followed by the evaluation of root number, root length, shoot length, fresh and dry weight. The biometric data were statistically analyzed and regression curves constructed. The seeds showed reticulate seed coat with a micropylar (opened) and chalazal (closed) end; the embryo results a chlorophyllated tuberiforme structure called protocorm, which may have rhizoids, leaflets and is considered plantlet when it has root. Absence of sucrose or the highest evaluated sucrose concentration was detrimental for plant growth. The concentration of 27 g L-1 provided the highest in vitro growth enabling great efficiency for mass propagation of this species of high ornamental potential.