Comparative effects of chloride and sulfate salinities on two contrasting rice cultivars (Oryza sativa L.) at the seedling stage

In field conditions, soil salinity may be due to an excess of different soluble salts. In order to compare the impact of chloride and sulfate salinities on rice, two contrasted cultivars (IKP: salt-sensitive and Pokkali: salt-resistant) were exposed to iso-strength Na+ nutrient solutions (NaCl 50 mM or Na2SO4 25 mM; EC: 5.31 dS m(-1)) for 2 weeks under controlled environmental conditions. It was found that NaCl was more toxic than Na2SO4, especially for the salt-sensitive IKP. Sodium and proline accumulation were higher while shoot osmotic potential was lower in NaCl-treated plants than in those exposed to Na2SO4. Chloride-treated plants exhibited a higher shoot malondialdehyde concentration, suggesting a higher level of lipid peroxidation while Na2SO4-treated plants presented a slightly higher total antioxidant activity. Pokkali was more tolerant than IKP to both types of toxicities although it accumulated similar concentration of toxic ions. Pokkali was able to reduce the root osmotic potential and to quickly recycle oxidized glutathione to reduced glutathione, which may help the plant to more efficiently control its oxidative status in stress conditions. It is concluded that different salts may have distinct impacts on the plant physiology and that differences may vary according to the considered cultivar.