Positive effect of AgNPs and AuNPs in in vitro cultures of Lavandula angustifolia Mill.

The aim of this study was determined how an addition of gold nanoparticle (AuNPs) and silver NPs (AgNPs) into culture media affects plant development and formation of oil glands in narrow-leaved lavender (Lavandula angustifolia) cv. 'Munstead'. Plant shoots were propagated on media supplemented with 1, 2, 5, 10, 20 and 50 mg dm(-3) AuNPs or AgNPs (diameter of 24.2 +/- 2.4 nm and 27.5 +/- 4.8 nm). Both of NPs positively influenced the growth and development of lavender propagated in vitro. The culture media with NPs stimulated formation of shoots and increased plant weight. Roots of plants propagated on the media supplemented with NPs were usually longer than those in the control. Only high concentrations of NPs (20 and 50 mg dm(-3)) in the culture media were toxic to plants, as demonstrated by restricted shoot length and gradual decrease in the value of other morphological features. Increases in AgNPs concentration caused the number of secretory trichomes to decrease. The diameter of the trichomes on both sides of the leaf blade was larger when the plants were propagated on the media supplemented with 1 and 2 mg dm(-3) NPs. The diameter of trichomes formed on the adaxial surface of the leaf blade was greatest in the media enriched with 2 mg dm(-3) AgNPs and 5 mg dm(-3) AuNPs, and smallest in the media enriched with 5 mg dm(-3) AgNPs. The diameter of trichomes formed on the abaxial surface was largest in plants exposed to 1, 2, 5 and 10 mg dm(-3) AuNPs, 1 mg dm(-3) AgNPs, and smallest in plants exposed to 5 mg dm(-3) AgNPs. Key message Silver and gold nanoparticles had a significantly improved the growth and development of narrow-leaved lavender propagated in vitro. The number and size of secretory trichomes formed on the leaves of narrow-leaved lavender grown in in vitro cultures depends on the concentration of silver or gold nanoparticles in the media.