The glandular trichomes of the Labiatae. A review

The species belonging to the Labiatae family are characterised by the presence of glandular trichomes. The most common and most described of these glands are peltate and capitate hairs. The first are considered the site of production and storage of essential oil; concerning the second, there is uncertainty about the chemical composition of the secretion, which probably contains polysaccharides and small quantities of essential oil. However, there are plants, lacking peltate trichomes, that produce essential oil in particular types of capitate trichomes. In this work is presented a short overview of the different types of trichomes present in the Labiatae family; utilising the histochemical stains and the ultrastructure of the secreting cells, the kind of secretion in each type of trichome is evidenced.