Light sources and culture media in the in vitro growth of the Brazilian orchid Microlaelia lundii

Abstract

The Brazilian micro-orchid Microlaelia lundii enchants by its beautiful blooms in winter, but its cultivation is still a challenge, requiring specific care. The objectiv of this work was to evaluate the influence of light sources and culture media on in vitro growth and ex vitro survival of this micro-orchid. M. lundii seedlings were transferred to flasks containing the culture medium ½ MS and Simplified Medium, consisting of 5 mL L-1 of Biofert Plus® NPK fertilizer (09-08-09) and 60 g L-1 of ‘Nanica’ banana pulp. These flasks were placed in a growth chamber composed of seven environments, characterized by types of lighting: L1) LEDtube 4000K; L2) LEDtube 6500K; L3) L1 + L2; L4) L1 + L1; L5) red LED; L6) blue LED; L7) fluorescent lamp (control). After 200 days of cultivation, biometric growth parameters and leaves chlorophyll content were evaluated together with the percentage of seedling survival when acclimatized. At the end of the experiment, an analysis of individual variances and a combined analysis of the environments were carried out. The simplified medium led to higher seedlings, especially for light source L6. Light sources L1, L2, L3 and L4 promoted an increase in the seedlings root system in the simplified medium. As for the chlorophyll content, L4 and L7 showed higher contents of chlorophyll a and b. The simplified medium led practically to 100% of seedling survival, regardless of the light source used. Results shown that the simplified medium for light sources L1, L2, L3 and L4 is recommended for the in vitro propagation of M. lundii.