Abstract
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.
Highlights
The family Orchidaceae has plants with greatly diversified flowers; there are about 800 genera containing 35,000 described species, valued for the beauty and durability of their flowers, which exhibit a wide variety of size, shape, colouration and fragrance (ROBERTS; DIXON, 2008).The genus Cattleya includes epiphytic orchids, with more than 113 species found from Central America to the south of South America
The analysis of variance relative to the data shows, that for all the variables analysed, there was a significant effect at 1% from the environment (ENV) and its interaction with 6-benzylaminopurine (BAP) and naphthaleneacetic acid (NAA)
For length of stem segment (LSS) was there a significant effect from the levels of BAP; there was a significant effect from the levels of NAA for all variables, except for the number of nodes per shoot (NN/S)
Summary
The genus Cattleya includes epiphytic orchids, with more than 113 species found from Central America to the south of South America. They are considered the “Queens of the Orchids” because of their large, colourful and showy flowers (BERKA; VENTURIERI; TEIXEIRA, 2014; CABRERA; CÚDOM, 2013). Noteworthy among these species is Cattleya labiata, native to the northeast of Brazil. The propagation of orchids occurs from shoots or by the natural dissemination of the seeds contained in capsules. Considering the difficulty of seminiferous multiplication in orchids due to delay and the necessity of the presence of mycorrhizal fungi, in vitro germination and cultivation are necessary
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