Abstract
Grapevine seedlings<em> Vitis vinifera</em> 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.
Highlights
IntroductionExtreme temperatures and excessive salinity may cause oxidative stress in plants
Water deficit, extreme temperatures and excessive salinity may cause oxidative stress in plants
The experimental conditions were as follows: control 1 (C1) plants were grown under optimum conditions for a week, S plants were grown under drought stress for a week, control 2 (C2) plants were grown for two weeks under optimum conditions, stress period (S+R) plants were grown for one week under drought stress and afterwards, for another week, under optimum conditions
Summary
Extreme temperatures and excessive salinity may cause oxidative stress in plants. In order to avoid it, plants have developed a complex system of antioxidative defence, which can be regulated depending on the environmental conditions. Excess of reactive oxygen species and free radicals generated by oxidative stress can be neutralized by plants in a number of ways. One possible defence mechanism involves scavenging systems, such as superoxide dismutase as well as catalyse and peroxidase. Another system employs small molecule compounds, such as glutathione, ascorbate, carotenoids, flavonoids, tocopherols, phenols, proline, etc., for neutralisation of reactive oxygen species and free radicals. Depending on the type of stress and affected organ, plants can activate different antioxidative mechanisms. It should be noted here that scavenging systems can be an important element of the processes which condition plant tolerance to stress (Qureshi et al 2007; Weidner et al 2007; Wony and Przyby3 2007)
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