Abstract
The research has been performed on roots of <em>Vitis vinifera</em>, cv. Himrod, obtained from seedlings grown under chill stress conditions (+10<sup>o</sup>C in the day and +7<sup>o</sup>C at night), under optimum conditions (+25<sup>o</sup>C in the day and +18<sup>o</sup>C at night) and from seedling which underwent a recover period after the chill stress treatment. The purpose of the study has been to determine quantitative and qualitative changes in phenolic compounds as well as to demonstrate changes in antiradical properties of extracts from grapevine roots, which appeared as a result of chill stress and during recovery under the optimum conditions following the stress. Phenolic compounds from grapevine roots were extracted using 80% acetone. The total content of phenolics was determined by colorimetry. The content of tannins was tested by precipitation with bovine serum albumin. The reducing power as well as DPPH• free radical and ABTS+• cation radical scavenging activity of the extracts were also tested. In order to identify phenolic compounds present in the extracts the RP-HPLC technique was employed. The tested material was found to contain tannins and three identified phenolic acids: ferulic, caffeic and p-coumaric ones. The latter occurred in the highest concentrations (from 4.46 to 6.28 µg/g fresh matter). Ferulic acid appeared in smaller amounts (from 1.68 to 2.65 µg/g fresh matter), followed by caffeic acid (from 0.87 to 1.55 µg/g fresh matter). Significantly less total phenolic compounds occurred in roots of seedlings subjected to chill stress. However, the total content of these compounds increased significantly in roots of plants which underwent recovery after chill stress. Concentration of tannins was determined by two methods. The content of condensed tannins was depressed in roots as a result of low temperature stress, whereas the content of condensed and hydrolysing tannins (determined via the BSA method) rose under chill stress conditions. A significant increase in tannins in root extracts (determined with both methods) was found during the recovery process after the stress. The three identified phenolic acids appeared in grapevine roots as ester-bound compounds. It has been demonstrated that the content of phenolic acids significantly fell as a result of low temperatures, but increased during recovery after chill stress. The weakest ability to scavenge DPPH• and ABTS+• free radicals as well as the reducing power were shown by the extract obtained from grapevine roots from the seedlings subjected to chill stress. Both free radical scavenging activity and reducing power were observed to increase considerably during recovery after stress. This seems to prove that during the recovery process following chill stress the synthesis of antioxidative compounds in grapevine roots is much more intensive.
Highlights
Good growth and development of plants depends on suitable environmental conditions
Dry matter content The results prove that dry matter in roots of grapevine seedlings subjected to chill stress (S) was significantly depressed compared to the control sample (C1), for which the dry matter content was 13.34% (Fig. 1)
Analysis of the results shows that the total phenolics in grapevine roots after chill stress (S) are significantly lower according to several calculations (339.44 mg/g of the extract, 56.91 mg/g of the dry matter, 5.27 mg/g of the fresh matter) versus the control sample (C1)
Summary
Good growth and development of plants depends on suitable environmental conditions. Air humidity, soil moisture, external temperature, light intensity and chemical composition of the substratum are important in this respect. CHANGES IN PHENOLIC COMPOUNDS FROM GRAPEVINE ROOTS ling has an immediate effect on membrane fluidity and enzyme kinetics, thereby influencing many cellular processes (Levitt 1980; Guy 1990). Abiotic stress factors such as shortage of water, extremely high or low temperatures or excessive salinity cause similar effects to those resulting from tissue damage or secondary stresses like osmotic or oxidative stress (Kmieæ et al 2005). Plant phenolics, including phenolic acids, are widespread secondary metabolites, which have been shown to give defence against oxidative stress from endogenous ROS and FR (Choi et al 2006; Kim and Chung 2002)
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