Reducing properties, and markers of lipid peroxidation in normal and hyperhydrating shoots of Prunus avium L.

The amounts of some reductants (ascorbic acid, reduced glutathione, cx-tocopherol) and the amounts of some markers of lipid peroxidation (peroxide and malondialdehyde) were quantified weekly in normal shoots (NS, in culture on agar) and in hyperhydrating shoots (HS, in culture on gelrite) of Prunus avium L. The redox activity of the plasma membrane (reduction of exogenously added ferricyanide), the antilipoperoxidant potential, the level of hydrogen peroxide and the lipoxygenase (EC 1.13.11.12) activity were investigated after 28 days of culture in both types of shoots. Reducing capacity of HS seemed generally more efficient in comparison to NS: higher levels of free ascorbate, reduced glutathione and the antilipoperoxidant potential were measured in HS than in NS. The alpha-tocopherol content did not change between the two types of shoots Reduction of exogenously applied ferricyanide was lower in HS during the last 2 weeks of the culture. These results suggest that the plasma membrane of HS had an unchanged reducing capacity but less redox transfer activity in comparison to NS. Markers of membrane damage (peroxide and malondialdehyde) were lower in HS than in NS and the same level of hydrogen peroxide was measured in the two types of shoots. Therefore, HS seem not to be submitted to oxidative stress. However, a more important lipoxygenase activity measured in HS was in contradiction to the lower peroxidation of lipids. The discussion points out some paradoxical results in an extensive classical analysis of stress criteria and indicates alternative defense mechanisms