Instability of morphological features used for classification of Thymus pulegioides infraspecific taxa

The stability of morphological features, traditionally used for the infraspecific classification of Thymus pulegioides L., was studied. The individual plants of T. pulegioides were collected from different habitats and cultivated under the same field conditions by cloning them annually for five years. The results of the cultivation experiment indicated that most of the investigated morphological features including length of leaves, length/width ratio of leaves and length of inflorescences were unstable. A conclusion was approached that the natural variation of the investigated morphological characters of T. pulegioides is not genetically fixed. It is phenotypic plasticity of plants, which depends on environmental conditions. Therefore the morphological characters, used at the “traditional” infraspecific classifications of T. pulegioides, cannot be used as the reliable diagnostic indicators of the infraspecific taxa of the species

The evaluation of phenotypic diversity of Thymus × Oblongifolius according to some anatomical characters and comparison with parent species

Lower and upper epidermises of leaves of interspecific hybrids Thymus × oblongifolius Opiz and its parent species — Thymus pulegioides L. and Thymus serpyllum L. — were studied using light microscope. The density of stomata and glandular trichomes, the diameter of glandular trichomes and the number of epidermal cells around the one glandular trichome were measured. The big diversity of investigated anatomical features was characteristic for T. × oblongifolius plants. The density of stomata and glandular trichomes distinguished for big diversity particularly. The stomata density on lower epidermis and the number of epidermal cells around the one glandular trichome on both epidermises of the interspecific T. × oblongifolius hybrid stood an intermediate position compared with those of parent species. The glandular trichomes density on upper and lower epidermises put together of leaves was major at T. × oblongifolius than at T. serpyllum and T. pulegioides , however the diameter of hybrids glandular trichomes was less than at parent species