Salicylic Acid Improves Cold Resistance of Solanum tuberosum Regenerants via Regulation of the Antioxidant System

Pretreatment of roots with salicylic acid (SA) and its role in control over morphophysiological parameters characterizing cold resistance of plant regenerants were examined in potato (Solanum tuberosum L.). It was found that potato plants exposed to low above-zero temperatures (4°C, 3 days) failed to restore initial growth parameters (plant height, leaf surface area, number of stolons, and weight of the organs) and oxidative status (intensity of lipid peroxidation) of the roots and leaves after transfer to favorable conditions (22°C, 10 days). A short-term (4-h-long) pretreatment of the roots with 0.1 µM SA minimized the adverse effect of deferred chilling. SA treatment promoted restoration of the initial plant phenotype after hypothermia, which caused a rise in growth parameters (number and surface area of the leaves and number of stolons) as compared with plants exposed to chilling without SA treatment. It was shown that pretreatment with SA improves cold resistance of potato plants owing to changes in the activity of antioxidant enzymes (superoxide dismutase and guaiacol-dependent peroxidase) and in the level of nonenzymatic antioxidants (ascorbic acid, anthocyans, total flavonoids and phenolic compounds). Depending on conditions, SA alters the ratio between individual flavonoids in the leaf. An ambiguous response to chilling and SA treatment was observed in two lines of potato regenerants produced by means of in vitro microcloning from the apical and middle part of the shoot, which is probably associated with their differing hormonal status.