Characterization of peltate trichomes of commercially important Lamiaceae species grown in Serbia

Abstract

Peltate trichomes have been the focus of botanical research for decades as the main secretory structures responsible for the production of essential oil and other specialized metabolites. For this study, samples of the plant material were obtained from the collection of the Institute for Medicinal Plant Research “Dr. Josif Pančić”. This study was conducted to perform morphological characterization, determination of the diameter and analysis of the distribution of peltate trichomes on leaves and calyces of selected commercial Lamiaceae species. In addition, the density of peltate trichomes on the leaves was determined. The analyses were carried out using a stereomicroscope and a scanning electron microscope. The leaves of all plant species bear peltate trichomes on the adaxial and abaxial leaf sides, with the highest density observed in Origanum heracleoticum (24.3 and 17.4 per mm2, re­spectively). Density was generally higher on the adaxial surface, with the exception of Mentha × piperita (higher density on the abaxial side) and Satureja montana (equal density on both leaf sides). The largest diameter of peltate trichomes was observed in leaves and calyces of S. montana (88.79 μm and 90.57 μm, respectively), while the smallest diameter was noticed in Origanum vulgare (about 65.00 μm). The plant species studied differ in appearance, diameter, distribution and density of the peltate trichomes. The results obtained indicate that micromorphological features could be valid parameters for the microscopic authentication of aromatic plants of which the representatives of the Lamiaceae are of par­ticular commercial importance.