| Abstract [eng] |
Master’ thesis by Laurita Rožytė ‘‘The Impact of Leaf Epidermal Anatomical Parameters on the Essential Oil Quantity in Thymus pulegioides Plants’’. Scientific supervisor dr. Kristina Ložienė, Vilnius University, Faculty of Medicine, Institute of Biomedical Sciences (Pharmacy and Pharmacology Center), 2024. Aim of the study: To investigate the connection between the essential oil quantity and leaf epidermal anatomical structures of Thymus pulegioides directly and indirectly related to the synthesis and accumulation of the essential oil. Objectives of the study: 1. To estimate and compare the essential oil quantities in T. pulegioides plants. 2. To determine which group of chemotypes (phenolic or non-phenolic) the investigated T. pulegioides plants belong to. 3. To estimate and compare the density of glandular trichomes and stomata on the upper and lower epidermis of leaves of T. pulegioides. 4. To estimate and compare the diameter of glandular trichomes on both sides of leaves of T. pulegioides. Methods of the study: The flowering aerial parts of the 27 T. pulegioides plants were collected separately from 5 natural habitats and dried. The assignment of T. pulegioides individuals to the group of phenolic or non-phenolic chemotypes was carried out organoleptically according to the smell of the raw material and/or the extracted essential oil. The essential oil from T. pulegioides plants was extracted by hydrodistillation and its content was expressed as a percentage. For the investigation of glandular trichomes and stomata anatomical preparations of the upper and lower epidermis of T. pulegioides leaves were prepared by the impress method, microscopy was done with a Leica DM5000 microscope. To estimate the size of glandular trichomes their diameter was measured in the upper and lower epidermis of leaves. To estimate the density of glandular trichomes and stomata their quantity per mm2 was calculated in the upper and lower epidermis of leaves. Statistical analysis was done using MS Excel 2023 and STATISTICA® 7 programs. Results and conclusions of the study: The essential oil amount in the investigated T. pulegioides plants was 0.60 ± 0.35 %. The essential oil percentage in the plants of phenolic chemotypes (0.78 ± 0.31 %) significantly (p < 0.05) differed from the essential oil percentage in the plants of non-phenolic chemotypes (0.45 ± 0.36 %). The density of glandular trichomes was significantly (p < 0.05) major in lower epidermis than in upper epidermis of leaves (6.7 ± 1.6 and 5.8 ± 1.3 glandular trichomes/mm2, respectively). A statistically significant positive correlation (r = 0.469, p < 0.05) was found between total number of glandular trichomes per mm2 of leaf area and essential oil percentage. The diameter of glandular trichomes was significantly (p < 0.05) major in upper epidermis (63.0 ± 2.3 µm) than in lower epidermis of leaves (61.4 ± 2.0 µm). There the diameter of glandular trichomes of individuals of phenolic chemotypes in upper and lower epidermis of leaf was significantly (p < 0.05) major (63.2 ± 2.6 and 61.5 ± 2.3 µm, respectively) than diameter of glandular trichomes of individuals of non-phenolic chemotypes (62.1 ± 1.3 and 61 ± 1.5 µm, respectively). No statistically significant correlation was found between essential oil percentage and diameter of glandular trichomes. Stomata density was three times major in lower epidermis and significantly (p < 0.05) differed from density in upper epidermis (380.3 ± 40.6 and 142.4 ± 33 stomas in 1 mm2 leaf area, respectively). No correlation was found between stomata density and essential oil percentage, however, statistically significant correlation (r = 0.399, p < 0.05) was found between the total number of stomata in mm2 of leaf area and the density of glandular trichomes in lower epidermis. |
