Cattleya walkeriana is one of the most important orchids in the world and has high ornamental value. Micropropagation plays an important role in the reproduction of this species. Based on high production costs of the standard micropropagation regarding the losses during acclimatization and high energy consumption in growth chambers, this paper aimed at evaluating alternative strategies for the in vitro cultivation. Two different factors were tested: light (standard growth chamber, greenhouse with 50% shading, and greenhouse without shading) and sucrose concentrations (0, 15, and 30g.L-1). The material was composed by plantlets previously germinated in vitro on MS medium and cultivated in a growth chamber for 90 days. Natural light in greenhouse induced an increase in the number of shoots, leaf thickness, stomata frequency and diameter and, on the other hand, caused decrease in the plantlet length and chlorophyll levels. Lower number of roots and shoots were formed at the concentration of 15g.L-1 sucrose. The absence of sucrose resulted in lower chlorophyll levels. Based on these results, it was possible to conclude that the cultivation environment modifies the response of in vitro cultivated plantlets and the natural light and reduction of sucrose concentrations by half can be recommend for the micropropagation of Cattleya walkeriana, taking in consideration the propagation phases and their goals.
Orchid; light; micropropagation; anatomy
