Efekat zeolita na parametre antioksidativnog statusa kod paradajza (Solanum lycopersicum L.) i kukuruza (Zea mays L.) u uslovima suše

Taking into account climate change, which implies a precipitation decreasing and temperatures rising, drought has become a global problem that is considered to be relevant for a long time to come. In addition to the problems it creates in many spheres of life, drought is one of the most serious factors that negatively affects agriculture, given that insufficient water supply disrupts the growth and development of plants. The production of reactive oxygen species in drought conditions can cause an inbalance of cellular redox homeostasis in the direction of oxidation and lead to the formation of oxidative stress. The consequences of oxidative stress are structural and functional damages of cellular compartments which leads to disturbance of metabolism and cell function. A very important role in plant tolerance to drought stress has the antioxidant protection systems that inevitably include the enzymes superoxide dismutase, catalase, Class III peroxidases and ascorbate peroxidase, but also low molecular weight antioxidants such as ascorbate, glutathione phenol and carotenoids. In recent years, there has been a sharp increase in interest in the use of environmentally sound and non-invasive means to improve the water supply of plants, and much attention has been paid to the use of natural aluminosilicates, the most famous of which is zeolite. Although not numerous, there are studies that suggest that this natural mineral can significantly contribute to the improvement of the water regime of plants due to the binding properties and balanced release of water. In this PhD thesis, the subject of research included two plant species different in type of photosynthetic metabolism and adaptive drought adaptation strategies, namely tomatoes (Solanum lycopersicum L.) and maize (Zea mays L.). The focus of research was to examine the possibility of using zeolite to prevent or mitigate the effects of drought stress in tomato and maize plants, but also to examine the possible different response in relation to the plant species. The intensity of oxidative stress was analyzed on the basis of analysis of biochemical parameters of antioxidant metabolism. In addition, analyzes included physiological parameters related to photosynthetic metabolism (structural characteristics of stoma, photosynthesis and transpiration intensity, Rubisco content, photosynthetic pigment concentrations, relative water content) and anatomical-histological characteristics of leaves and shoot morphological properties. For the research with tomato plants zeolite was applied with three different concentrations (5%, 10% and 20%). Control plants were optimaly irrigated during the entire experimental period, without zeolite in substrate, but also with all applied zeolite concentrations. The plants in drought conditions were not irrigated and they were divided into group without zeolite and with 5%, 10% and 20% zeolite respectively. The obtained results showed that the addition of 5% zeolite to the substrate can significantly contribute to the mitigation of the negative effects of stress, although complete drought prevention has not been achieved. The zeolite application of 10% did not have a positive effect, while the application of 20% caused additional deteriotation of drought consequences. In that sense, it was concluded that the effect of zeolite on the antioxidant status of tomato plants in drought conditions is conditioned by its concentration in the soil, and that depending on it, it can be both positive and negative. In experiment with maize plants, two zeolite concentrations (5% and 10%) were applied. Control plants were irrigated without zeolite and with applied 5% and 10% zeolite respectively, while plants submitted to drought were not irrigated and they also were without zeolite and with selected concentrations. The results showed that the application of zeolite in any concentration cannot prevent or mitigate the effects of oxidative stress caused by drought in maize plants. In addition, physiological indicators and parameters of enzymatic antioxidant metabolism indicated that the presence of 10% zeolite further exacerbates drought-induced stress. The presence of zeolite in the substrate of maize plants was harmful even in conditions of optimal irrigation as a result of cation exchange with surrounding substrate and redistribution of chemical elements which conditioned the toxic effects of certain ions, but also the defficite of necessary ions for undisturbed metabolism. It was concluded that the biochemicalphysiological pathways in metabolic drought adaptation strategies differed somewhat in tomato and maize plants, and also that the effect of zeolite in preventing the effects of stress was species-specific and concentration dependent.