Micromorphological Traits of Balcanic Micromeria and Closely Related Clinopodium Species (Lamiaceae)

Abstract

A study of the trichomes types and distribution and pollen morphology was carried out in nine Micromeria taxa (M. cristata ssp. cristata, M. cristata ssp. kosaninii, M. croatica, M. graeca ssp. graeca, M. graeca ssp. fruticulosa, M. juliana, M. kerneri, M. longipedunculata and M. microphylla) and five closely related Clinopodium species (C. dalmaticum, C. frivaldszkyanum, C. pulegium, C. serpyllifolium and C. thymifolium) from the Lamiaceae family of the Balkan Peninsula. By scanning electron microscope, non-glandular trichomes, peltate and capitate trichomes were observed on the calyx, leaves and stem of the studied species. Two subtypes of capitate trichomes were observed in Micromeria species: subtype 1 (consisting of a basal epidermal cell and an elliptically shaped head cell) and subtype 2 (consisting of a basal epidermal cell, two to three stalk cells and a round head cell). In Clinopodium species, three types of capitate trichomes were observed: subtype 1, subtype 3 (consisting of a basal epidermal cell, a short peduncle cell, and a single round head cell), and subtype 4 (consisting of a basal epidermal cell, a stalk cell, and an elongated head cell). These results support the recent transfer of Micromeria species from the section Pseudomelissa to the genus Clinopodium.

Volatile Organic Compound Composition and Glandular Trichome Characteristics of In Vitro Propagated Clinopodium pulegium (Rochel) Bräuchler: Effect of Carbon Source

“…Pseudomelissa based on molecular and morphological/anatomical evidence [3]. Micromorphological traits support the transfer of Micromeria species from the section Pseudomelissa to the genus Clinopodium [4].…”

“…There are a few available contributions regarding the morphological and phytochemical characterization of the species. The micromorphological investigations of the vegetative and reproductive organs concerned trichome morphotypes, their distribution and abundance [4,5], and one study focused on the morphoanatomical and histochemical analyses of leaf glandular trichomes [6].…”

Clinopodium L. Taxa from the Balkans—Are There Unique Leaf Micromorphological and Phytochemical Patterns?

“…However, it is important to define which capitate trichomes contribute the most to variability. The trichome type with the shortest stalk, referred to as the C1a subtype in our study, is widespread in the family Lamiaceae, especially in the subfamily Nepetoideae [ 38 , 50 ]. The trichomes very similar to C1a are found in the subfamily Lamioideae [ 51 ].…”

“…Since the morphologically heterogeneous genera were transferred to Clinopodium , significant differences between the taxa groups were to be expected. However, the study by Kremer et al [ 50 ] supported the transfer of species from the section Pseudomellisa (broad-leaved species of the former genus Micromeria ) into Clinopodium . The authors argued the transfer with the fact that the section Pseudomellisa possesses an additional two types of capitate trichomes which are not noticed in typical, narrow-leaved Micromeria species.…”

Phytochemicals and Their Correlation with Molecular Data in Micromeria and Clinopodium (Lamiaceae) Taxa

“…Based on this view, Bräuchler et al [ 15 ] transferred the section Pseudomelissa from the genus Micromeria to the genus Clinopodium L. Bräuchler et al [ 1 ] also provided a comprehensive list of new combinations, synonyms, and valid names. Studies on micromorphological characters of Balkan Micromeria and closely related Clinopodium species support the recent transfer of the section Pseudomelissa into the genus Clinopodium [ 16 ].…”