Abstract
The aim of this study was to evaluate different concentrations of two cytokinins in the in vitro propagation of the medicinal plant Hyptis marrubioides Epl. and to analyse the volatile fraction of the compounds. Nodal segments of plants were inoculated onto Murashige and Skoog (MS) solid medium with different concentrations of benzylaminopurine (BAP) or tidiazuron (TDZ) under a 16/8 h light/dark cycle at 25 ± 2 °C. After 45 days growth, the plants were evaluated for the number and length of the shoots and for shoot dry matter. The volatile constituents were analysed by headspace-GC/MS. The greatest number of shoots was obtained with 1.0 mg L-1 TDZ in the MS medium. The greatest values for shoot length and dry matter were obtained with BAP. Twenty-seven compounds were characterised as constituents of the essential oil of H. marrubioides. The major compounds of the volatile fraction were sabinene, α-thujone, β- thujone, α-copaene, β-caryophyllene, γ-gurjunene and γ-himachalene. The types and concentrations of the growth regulators influenced accumulation of the volatile fraction. Quantitative changes in the monoterpenes and sesquiterpenes in the volatile fraction of the plants were also seen in response to the type of growth regulator added to the culture medium.
Highlights
Hyptis marrubioides Epl. (Lamiaceae) occurs in the phytogeographical domains of the Cerrado and Atlantic Forest, and is found in the States of Minas Gerais and Goiás, Brazil (HARLEY et al, 2012)
It was found that TDZ was more efficient than BAP for number of shoots; the greatest shoot lengths and dry-matter volume were seen with the presence of BAP (Table 1)
The results indicate that the application of growth regulators can affect the production and composition of the essential oil, which corroborates research reported by other authors (HAZZOUMI et al, 2014; NOURAFCAN et al, 2014)
Summary
Hyptis marrubioides Epl. (Lamiaceae) occurs in the phytogeographical domains of the Cerrado and Atlantic Forest, and is found in the States of Minas Gerais and Goiás, Brazil (HARLEY et al, 2012). H. marrubioides is propagated preferentially by seeds; for medicinal aromatic plants, sexual reproduction by allogamy results in plants of more-variable morphology and the production of secondary metabolites. Plant tissue culture allows better control of environmental factors, since suitable conditions can be ensured, such as luminosity, concentration, type of culture medium and growth regulator, in order to obtain suitable conditions for growth and multiplication. Among the growth regulators are the cytokinins, compounds which favour multiplication, promoting an increase in the number shoots per explant through the fall of apical dominance and the proliferation of meristematic zones (KYOZUKA, 2007). In Passiflora foetida L., Shekhawat et al (2015) reported a greater number of shoots with 2 mg L-1; in Baco pamonnieri, a concentration of 0.10 mg L-1 was the most suitable for the multiplication of the species (SHARMA et al, 2010)
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