Stem and Leaf Anatomy of Three Taxa in Lamiaceae

Stem and leaf anatomy of Origanum rotundifolium Boiss., O. vulgare L. ssp. viride (Boiss.) Hayek, Teucrium hircanum L., belonging to Lamiaceae were characterized and compared. Some important differences were determined in the taxa. In addition, trichome diversity was investigated by light microscopy and three main types of trichomes (peltate, capitate glandular and non-glandular) were observed in three taxa. Introduction The Lamiaceae is a large family which is represented by about 258 genera and 3500 species in the world (Duarte and Lopes 2007). It is the third largest family in Turkey with 45 genera and 574 species of which 256 are endemic (Güner et al. 2000) and the country is regarded as a gene center for this family (Başer 1993). Origanum L. genus is represented by 25 taxa in the Turkish flora (Güner et al. 2000). Almost a half of them (12) are endemic to Turkey. Some species contain phenolic substances such as carvacrol and thymol. Thymol is also used as a starter in the synthesis of some pharmacological active ingredients, for tooth filling, in the preparation of antiseptic baths and soaps and in the preservation of some foods (Baytop 1999). Teucrium L. is a large and polymorphic genus of the Lamiaceae. The genus Teucrium comprises totally 44 taxa belonging to 8 sections in Turkish flora (Yildirimli 2008). Trichomes are among the most useful taxonomic characters in Teucrium L. (Navarro and El Oualidi 2000) described infrageneric relationships between sections depending on trichome types. Many species of Lamiaceae have been used as herbal teas in Turkey and most of them have great importance due to their economic values and many of them are used as raw material in cosmetic industry. Some species are used in official and traditional medicines in Anatolia, Europe and China (Baytop 1999, Cui et al. 2003). Some species are cultivated as ornemantal plants (Rudy 2004). The morphology and anatomy of several species have been studied so far (Tahir et al. 1995). In Lamiaceae, the systematic value of trichome types was demonstrated by Abu-Assab and Cantino (1987) in the subtribe Melittidinae (Dumort.) Endlicher. Glandular trichomes producing essential oils of commercial value are widespread on leaves and fowers of the Lamiaceae and their structures have been examined anatomically and micromorphologically by several authors (Akçin et al. 2011, Kaya et al. 2007). In recent years, anatomical characters have been used in taxonomy (Agbagwa and Ndukwu 2004, Kharazian 2007, Eminagaoglu et al. 2012, Ozcan et al. 2014). The main object of this study is to investigate detailed description of anatomical structures of the stem and leaf in three Lamiaceae taxa by using light microscopy. The variation in leaf characters is discussed with respect to their potential systematic value and in relation to our previous work. *Author for correspondance: . Department of Forest Engineering, Faculty of Forestry, Artvin Coruh University, 08000 Artvin-Turkey. 346 OZCAN AND EMINAGAOGLU Materials and Methods Plant samples were collected from Artvin Province and dried according to herbarium technigues and stored in Artvin Coruh University Herbarium (ARTH). The localities and collection data are listed in below. Origanum rotundifolium Boiss.; A8 Artvin: Yeni mahalle (İskebe), stony slope, 500 m, 08.vii.2011, Ö. Emin. 8836. O. vulgare L. ssp. viride (Boiss.) Hayek; A8 Artvin: Hatila Valley National Park, roadside, 570 m, 08.vii.2011, Ö. Emin. 8839. Teucrium hircanum L.; A8 Artvin: Hatila Valley National Park, roadside, 600 m, 08.vii.2011, Ö. Emin. 8838. Anatomical investigations were carried out on the cross-sections of the upper and lower stems, the leaves and surface sections of the leaves. All sections were prepared manually and stained with Hematoxyline solution. They are preserved on the permanent slides in glyceringelatin solution. The photographs of the sections were taken using an Olympus BX-53 research microscobe with digital camera attachment DP-73. Five cross-sections from at least three different individual plants of each taxon were measured for each sample to assess the consistency of anatomical characters. Ten peripheral slides were prepared for each taxon and 50 stomatal lengths were measured on each slide. The stomatal index was calculated. Results and Discussion In this study, three taxa belonging to Lamiaceae were investigated and their anatomical characters are represented here for the first time from Turkey. Two of the investigated taxa belong to the genus Origanum and one species belongs to the Teucrium. Cross sections in the middle parts of stems and transverse section of the lamina, midrib and both epidermises of leaf were investigated, and representative anatomical characters are summarized in Tables 1 and 2. Table 1. Stem features of three Lamiaceae taxa. Characters O. rotundifolium O. vulgare ssp. viride T. hircanum Epidermis length (μm) 14.47 ± 0.59 13.53 ± 0.84 14.53 ± 0.34 Epidermis width (μm) 25.73 ± 1.12 19.00 ± 0.57 20.87 ± 1.48 Cortex thickness in the corner (μm) 201.93 ± 19.84 143.40 ± 4.85 203.40 ± 5.14 Number of cortex layer 12 13 11 14 1215 Corner collenchyma thickness (μm) 112.73 ± 10.88 71.60 ± 7.67 125.00 ± 4.37