Morfofiziološke osobine paradajza u uslovima povećanog saliniteta / Morph physiological features of tomatoes grown in conditions of increased salinity

Stress conditions often occur during the tomato production in greenhouses due to increased substrate salinity, which is the result of intensive fertilization, use of inadequate water for irrigation and impossibility of natural soil rinsing. One of the widely used methods by which the problems of plant cultivation under increased salinity can be overcome, and which has no harmful effects on the environment, is grafting. Therefore, the aim of this research was to examine the level of morphological, biochemical and physiological changes occurring in two tomato hybrids (Buran F1 and Berberana F1) grown from grafted and non-grafted seedlings in the presence of different salt concentrations (EC 1.7 dS m-1 (control), 3.8 dS m-1 (S1), 6.9 dS m-1 (S2) and 9.1 dS m-1 (S3)). Twelve weeks after planting, in fruiting phenophase, intensity of photosynthesis, transpiration and gas exchange through stomata were measured. Leaves were sampled and the activities of antioxidant enzymes (SOD, ascorbate peroxidase and class III peroxidase) in them was assessed. The weight of fully mature fruits from the first fruiting branch (sampled at the same time as the leaves) was measured and the concentrations of lycopene, ascorbic acid, phenolic compounds and total antioxidant capacity were measured in them. Different levels of substrate salinity in experiments led to significant changes in the growth and metabolism of the examined tomato hybrids. The difference in the reaction of grafted and non-grafted tomato hybrids to S1, S2 and S3 was found. SOD and ascorbate (AA) played a key role in the antioxidant protection, while in the long-term response of tomatoes to S1, S2 and S3, during the ripening phase, the role of peroxidases was less significant. Inter-hybrid differences in SOD and AA activity was also found. During the twelve weeks of exposure of tomato plants to salt treatments, the plants adapted well, as indicated by the increased AA content, as well as the AA/DHA ratio, which is probably the result of rapid AA regeneration. Moreover, the concentration of nonenzymatic antioxidant components in the leaves and fruits of both examined hybrids, was lower in grafted plants, at all levels of increased substrate salinity. The average weight of fruits of grafted plants, depending on the level of substrate salinity, was 40% to 60% higher compared to the non-grafted, which is very important for the market value of tomato production. The results of this dissertation have made it possible to perceive and quantify the effect of grafting on tomato tolerance towards the increased salt concentration in the substrate, which is very important for the successful production of this vegetable.