An investigation of the effects of drought and salt stresses on the physiological and biochemical characteristics of the endemic taxa cephalaria duzceensis N. Aksoy & R. S. Göktürk and Seseli resinosum Freyn & Sint.

Endemic species are local and rare organisms that spread only in certain parts of the earth. The province of Düzce has a very rich floristic structure in terms of herbaceous and woody endemic plants. Since some species are extinct, it is important to ensure the sustainability of endemic plant species in Düzce and its environs. The aim of this thesis was to determine the potential of growing herbaceous plants Cephalaria duzceensis N. Aksoy & R. S. Göktürk and Seseli resinosum Freyn & Sint. which are endemic and endangered species in Düzce and to determine the growing in different medium and adaptation potentials to environmental stresses within the scope of ex-situ conservation studies. Tolerance processes under two abiotic stresses which caused product and yield losses by negatively affecting the growth and development of the plant such as drought and salinity were tried to be clarified. Drought and salt stresses cause secondary stresses such as ionic, osmotic, hormonal and nutritional imbalances in plants and consequently oxidative damage results in the accumulation of reactive oxygen species (ROS). Physiological and biochemical properties of these endemic plants were determined in order to determine the resistance performance and provide the exact growing medium of these plants against oxidative damage. The responses of these endemic plants under drought and salt stresses were determined by measuring growth parameters, physiological parameters such as leaf relative water content, osmotic potential, photosynthetic yield and biochemical parameters such as lipid peroxidation, hydrogen peroxide, proline and antioxidant defense system enzymes (superoxide dismutase (SOD; EC 1.15.1.1) , peroxidase (POX; EC 1.11.1.7), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11), glutathione reductase (GR; EC 1.6.4.2)). As a result, it was found that Cephalaria duzceensis N. Aksoy & R. S. Göktürk was more tolerant to drought stress with high POX, CAT and APX activities and Seseli resinosum Freyn & Sint. was more tolerant to salt stress with high SOD, POX and GR activities and reduced cell damage by activating antioxidant defense system under these stresses. Keywords: Cephalaria duzceensis, Drought stress, Endemic species, Salt stress, Seseli resinosum