Influence of culture medium components on in vitro propagation of Laelia gloriosa (Orchidaceae)

Abstract

The aim of this study was to evaluate the effect of commercial fertilizer, dual-phase cultivation with cytokinin and sucrose concentrations on the growth of the orchid Laelia gloriosa. Firstly, the effect of adding commercial fertilizer to the MS ½ basal culture medium was tested. The effect of concentrations of 6-Benzylaminopurine (BAP) was also analyzed: 0, 1.5 and 3.0 mg L-1 in semi-solid medium and liquid medium in two phases. Finally, whether or not the culture medium was supplemented with activated charcoal and sucrose (15; 30; 45 and 60 g L-1) was evaluated, followed by acclimatization. The growth variables analyzed were: aerial part and root system length, number of leaves and adventitious shoots, fresh biomass and the quantification of photosynthetic pigments. The results showed that supplementing the medium with fertilizer did not increase plant growth. The two-phase system was superior to the semi-solid system for the formation of adventitious shoots when supplemented with 1.5 or 3 mg L-1 of BAP. The growth variables were significantly influenced by sucrose, the formation of the root system was favored at the highest doses (45 and 60 g L-1) while the number of leaves was higher in the absence or at the lowest concentrations of the carbohydrate. Higher levels of chlorophyll a and b were obtained when the plants were grown in vitro with 45 g L-1 of sucrose. In ex vitro conditions, the highest survival rate and chlorophyll content was observed in a medium containing 30 g L-1 sucrose, guaranteeing a higher percentage of survival for plants.