High-salinity activates photoprotective mechanisms in Quercus suber via accumulation of carbohydrates and involvement of non-enzymatic and enzymatic antioxidant pathways

Cork oak (Quercus suber), native to Mediterranean areas, is a plant of ecological and economical relevance, nevertheless, the effects of soil salinization on this species are currently unknown. We have investigated the physiological and biochemical impact of a high-salinity episode on young cork oak (Q. suber) plants. Besides the control (plants only irrigated with water), two experimental groups (irrigated once with a 300 mM NaCl solution) were analysed, one assessed at 24 h and the other at 6 days. Pigments (chlorophylls and carotenoids) were found increased at 24 h, but decreased at day 6 in salinity conditions. Sugars (glucose, sucrose, starch but not fructose) increased with stress (24 h and 6 days). Salinity conditions impaired photosystem II (PSII) photochemistry, mostly associated with decrease in Fv′/Fm′ and chlorophyll content (6 days). While hydrogen peroxide levels did not increase above control levels, lipid peroxidation increased, suggesting oxidative damage. In salinity conditions, superoxide dismutase and ascorbate peroxidase showed higher activity in the 24 h timepoint, whereas catalase activity increased at 24 h and 6 days. These observations reveal adaptations of Q. suber to high salinity, nevertheless, the decreased photosynthetic activity and oxidative damages observed suggest that additional studies are required to assess Q. suber adaptation to diverse salinity conditions. Moreover, these data provide more information for future programs of conservation and management of salinity areas in the Mediterranean region, and selection of salinity tolerant species.