Inhibitors of Na/H Antiporter and Cation-Chloride-Cotransporters Have Contrasting Effects on Two Cultivars of Oryza glaberrima Steud. Differing in Salinity Resistance

A pharmacological study was conducted to analyze the impact of inhibitors of Na+-H+ antiporters (amiloride 100 µM) and cation-chloride-cotransporters (bumetanide 200 µM) on two cultivars of the African rice species (Oryza glaberrima Steud) differing in salt resistance (TOG5307: salt-resistant and TOG5949: salt-sensitive) exposed to 75 mM NaCl during 3 days. Amiloride increased Na+ accumulation in roots and leaves to a higher extent in salt-resistant TOG5307 than in salt-sensitive TOG5949. Bumetanide reduced Cl− accumulation in both cultivars as well as K+ accumulation in TOG5307 and Na+ accumulation in TOG5949, suggesting that the cation-chloride-cotransporter in O. glaberrima does not necessarily strictly behave as a Na+:K+:2Cl− transporter. Inhibitors mainly acted on the absorption step but had low impact on root-to-shoot translocation process. The salt-resistant cultivar TOG5307 was able to efficiently regulate Na+ uptake and to cope with high concentration of accumulated toxic ions, as demonstrated by a higher cell viability index and a higher concentration of protein and photosynthetic pigments in NaCl-exposed plants comparatively to salt-sensitive TOG5949.