Sodium benzoate inhibits germination, establishment and development of rice plants
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Sodium benzoate (NaB) is widely used as food and drink preservative. However, little is known about the phytotoxic effects of NaB on plants. The aim of this study was to evaluate the phytotoxicity effects of exogenous sodium benzoate on seed germination and seedling establishment of rice plants. Seeds were treated with 0, 5 and 10 mM of NaB in a growth chamber with controlled conditions. NaB decreased the germination rate, plant growth and biomass accumulation. Increasing NaB concentration resulted in disruption of cell membranes, disturbance of the plant water status and degradation of the photosynthetic pigments. In addition, NaB decreased photosynthesis and transpiration rates in rice seedling and triggered non-photochemical quenching (NPQ). The NPQ was able to avoid photoinhibition in rice seedlings exposed to NaB. On the other hand, the harmful effects were related with increases in the production of reactive oxygen species, primarily H2O2. Rice plants exposed to 5 mM NaB triggered antioxidant defenses with increased activities of superoxide dismutase (SOD), ascorbate peroxidases (APX) and catalase (CAT). In contrast, the exposure of 10 mM of NaB decreased the activities of these enzymes. Our data clearly show that NaB triggered phytotoxicity effects in rice seedlings, impairing growth, photosynthesis and development.