Grapevine seedlings Vitis vinifera L. were grown in a greenhouse under optimum conditions (soil moisture ca 70 %) and under drought stress (soil moisture ca 30 %). Drought stress caused reduction in total phenolic compounds in grapevine leaves and roots, where were identified tree phenolic acids: caffeic acid, p-coumaric acid and ferulic acid. All acids found in leaves and roots occurred in the ester-bound form. Only caffeic acid in leaves appeared in the free and ester-bound form. Caffeic acid was present in the highest concentrations. The content of ferulic acid was the lowest in both tissues. The levels of all phenolic acids in leaves and roots decreased significantly under the drought stress. All the extracts from grapevine leaves and roots had antioxidative properties, but the antiradical activity of the extracts obtained from roots subjected to drought stress was lower to the control. The results of the analysis revealed that long-term drought stress caused a decrease in selected elements of secondary metabolism in such a different plant tissues that are the leaves and roots of the grapevine.

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Grapevine seedlings Vitis vinifera were grown in a greenhouse under optimum conditions (soil moisture ca 70%) and under drought stress (soil moisture ca 35%). In addition, some of the plants subjected to drought underwent subsequent regeneration under optimum conditions. Drought stress caused accumulation of total phenolic compounds in grapevine roots, which may indicate that these compounds play an important role in the adaptation of roots to growth under stress conditions. Phenolic acids found in the roots occurred in the ester-bound form only. p-coumaric acid was present in the highest concentrations (6.2 to 10.5 µg/g fresh matter). The content of ferulic acid was lower, ranging from 2.4 to 4.6 µg/g fresh matter. The lowest concentration in grapevine roots was achieved by caffeic acid (2.4 to 2.9 µg/g fresh matter). The levels of p-coumaric and ferulic acids in roots rose significantly under the drought stress, while the concentration of caffeic acid increased during the post-drought recovery period. This may suggest that some of the phenolic acids protect plants under stress conditions. All the extracts from grapevine roots had antioxidative properties, but the antiradical activity of the extracts obtained from roots subjected to drought stress was inferior to the control. The same extracts were also characterised by depressed reducing power. The results imply that tolerance of grapevine to soil drought may be associated with the value of antioxidative potential in root tissues of these plants

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