Artificial light and growth regulators on the in vitro etiolation of Cattleya labiata

Resumo

The technique of etiolation is widely used in the micropropagation of various plant species. The aim of this study was to evaluate growth and development in shoots of Cattleya labiata grown in vitro, as a function of growth regulators and the presence and absence of light. Stem segments, approximately ± 1.0 cm in height, were inoculated in test tubes containing 15.0 mL of MS culture medium supplemented with different concentrations of BAP (0.0, 2.0 and 4.0 mg L-1) and NAA (0.0, 1.0 and 2.0 mg L-1), and in different growth environments (growth room, darkness and a photoperiod of 16 hours) in a completely randomised design. At 150 days, the following were evaluated: a) number of etiolated shoots; b) number of nodes per etiolated shoot; c) length of stem segment (cm); d) number of roots; and e) total seedling dry weight (g). The highest mean values were achieved with the use of 4.0 mg L-1 BAP and 1.0 mg L-1 NAA for the number of etiolated shoots, and 2.0 mg L-1 NAA for the number of nodes per etiolated shoot in the absence of light. The length of the main shoot was greater in the absence of light; in contrast, the number of roots and the total dry weight of etiolated nodal segments were greater in a bright environment, irrespective of the growth regulator added to the culture medium. The etiolation of stem segments is a viable technique, as it provides features that are advantageous in the in vitro multiplication stage of the species.