LAVANDULA PEDUNCULATA (MILLER) CAV.: TRICHOMES, ESSENTIAL OILS AND IN VITRO CULTURE

Abstract

The morphology and histochemistry of Lavandula pedunculata glandular trichomes as well as the chemical composition and intraespecific variability of its essential oils were investigated. The antifungal activity of the essential oils and their major compounds was evaluated against different pathogenic fungi. Moreover, in vitro cultures of axillary meristems were established and the influence of different concentrations of benzyladenine (BA) in the culture medium was analysed. SEM analysis showed the presence of three types of glandular trichomes: peltate, capitate type I and capitate type II, as well as a “mixed” type. Histochemical tests revealed a lipidic and terpenic secretion for all types of glandular trichomes, excluding the capitate type I. The essential oils of 43 samples of L. pedunculata from the north and centre of Portugal were isolated by water distillation followed by GC and GC/MS analysis. Quantitative differences were found, particularly in the amounts of 1,8-cineole (2.4 – 55.5 %), fenchone (1.3 – 59.7 %) and camphor (3.6 – 48.0 %). A significant antifungal activity was found against the dermatophyte strains. The essential oil with high contents of camphor was the most active with MIC and MLC values ranging from 0.32 – 0.64 µL/mL, justifying therefore, the use of these oils against dermatophytosis. In vitro cultures of axillary buds of L. pedunculata were established in MS medium supplemented with different concentrations of benzyladenine (BA). The production of axillary shoots was favored by the use of 0.25 mg/L of BA and the rooting was spontaneous. The in vitro plantlets showed an indument and an essential oil composition very similar to that of respective field-growing plants, and may be used for the same purposes as wild type plants.