Leaf trichomes of Portuguese Lavandula species: a comparative morphological study

Abstract Lavandula species are aromatic plants that produce and accumulate essential oils in different types of glandular trichomes. The oils protect the aerial parts of the plant against herbivores and pathogens, and are of great economic value for fragrance, pharmaceutical, food and flavour industries. In Portugal there are five spontaneous species of Lavandula which are included in three different sections: Section Lavandula (L. latifolia), Section Pterostoechas (L. multifida) and Section Stoechas (L. luisieri, L. pedunculata, L. viridis). Our preliminary observations showed that these species have a high diversity of trichomes. This, associated with the fact that trichome morphology is often referred as an useful characteristic for systematic purposes, led us to investigate leaf trichome morphology in the five Portuguese species, using scanning electron microscopy (SEM).