Cattleya orchids seedlings in vitro performance under artificial and natural light

Abstract

In vitro seed germination represents an important alternative to overcome limitations of the orchid conventional propagation. The use of natural light demonstrated potential in promoting in vitro hardiness of tropical orchid species, as well as reducing production costs. The goal of this study was to evaluate seedlings on in vitro growth of the native orchid species Cattleya amethystoglossa, Cattleya nobilior and Cattleya walkeriana under standard growth chamber and natural sunlight. Germinated protocorms (0.5 cm in length) in half-strength Murashige and Skoog culture medium in a growth chamber (30 μmol m-2 s-1 provided by fluorescent lamps in a 14-h photoperiod and temperature of 26±2°C) were subcultured in the same culture medium and incubated in the conditions of growth chamber or under natural light (80 μmol m-2 s-1 and 26±2°C). Seedlings growth characteristics of length and number of roots, shoot length, number of leaves, fresh weight, chlorophyll and carotenoid content were evaluated after 150 days. Data were statistically analyzed by ANOVA and means separated by Tukey’s test. Artificial light favored pigment accumulation. There were significant differences between species in all analyzed parameters, except for number and length of roots. Cattleya amethystoglossa and Cattleya nobilior presented similar or superior growth under natural light, while Cattleya walkeriana presented less growth efficiency for shoot length, leaf number and fresh weight. Seedlings were deflasked and successfully acclimatized in greenhouse conditions.