Antioxidant defense system based responses to drought stress of Helichrysum arenarium (L.) Moench (sandy everlasting) distributing in Sivas (Hafik, Olukbaşı) region

Morphological, physiological and biochemical studies of Helichrysum arenarium (L.) Moench (sandy everlasting) plant, which has medicinal and aromatic properties, under drought stress are not available in the literature. Helichrysum species are known as medicinal aromatic plants that are used in traditional folk medicine and continue to be used in modern medicine today. It is seen as a natural antioxidant due to its activities to prevent the formation of reactive oxygen species and other free radicals. For this purpose, it was tried to determine the morphological, physiological and antioxidant defense system-based responses to drought stress in the germination and early development period of sandy everlasting plant collected from Sivas region. Sandy everlasting seeds grown in petri dishes were exposed to drought stress (0-30%) with PEG-6000 in air-conditioning rooms where controlled conditions were provided. Growth parameters, leaf water content (YSI), thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H2O2) amount and antioxidant enzyme activities (superoxide dismutase (SOD)) of PEG-6000 (0-15%) applications during the early development period of sandy everlasting plants. catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR)) changes were investigated. In the germination study, it was determined that sandy everlasting seeds could not germinate in PEG 20% and PEG 30% media, and PEG 15% application in the early development period caused a serious suppression on the development of the seedlings. Drought treatment (PEG 5% and PEG 10%) caused a decrease in the growth parameters of sandy everlasting plants, YSI, CAT and GR levels, and an increase in TBARS, H2O2, SOD and APX values. In this thesis, it was demonstrated for the first time that the antioxidant enzymes APX and SOD activities increased, although the growth was suppressed when the severity of drought increased in sandy everlasting plants. Keywords: Sandy everlasting, Drought, Stress, H2O2, Antioxidant Defense System